JP2009008668A - Method and system for quantitative analysis of selenium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for quantitative analysis of the quadrivalent selenium concentration in drainage water, on site. <P>SOLUTION: The analysis method includes a closed type container 2 for receiving acid analysis sample 2a with the acid normality adjusted to 0.13-6.7 N/L, by adding at least either hydrochloric acid or sulfuric acid to the analysis sample with quadrivalent selenium existing in solution; a means 3 for adding sodium tetrahydroborate 3a to the acid analytical sample 1L at 5-10 g per minute or lower; a means for supplying carrier gas at 500-700 mL per minute; a potentiostat sensor 4 for measuring hydrogen selenide for outputting the measurement; a supply means for aspirating the hydrogen selenide generated from the acid analysis sample 2a, together with the carrier gas at 400-600 mL per minute and supplying them to the potentiostat sensor 4; and an analysis means 5 for analyzing the quadrivalent selenium concentration in the analytical sample from the measurement, based on the memorized calibration curve which has been generated, according to the correlation between the quadrivalent selenium concentration which has been previously calculated from a plurality of standard samples with their known quadrivalent selenium concentration and the measurement of the potentiostat sensor 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and system for quantitatively analyzing selenium. More specifically, the present invention relates to a quantitative analysis method and a quantitative analysis system suitable for on-site analysis of the concentration of selenium dissolved in water.

  Selenium (Se) is an element widely used in industry. For example, in addition to being used for glass colorants and decolorizers, it is used for photosensitive drums and rectifiers of copiers by utilizing the semiconductivity and photoconductivity of metal selenium.

  Under such circumstances, wastewater containing selenium may be discharged in the process of manufacturing industrial products containing selenium, or selenium may be eluted into the environment due to the use or disposal of industrial products containing selenium.

  Also in the field of electricity business, selenium may be contained in coal-fired power plant effluent and coal ash disposal site elution water due to the small amount of selenium contained in coal.

  Here, while selenium is an essential element of the human body, it is known as an element that causes neurological disorders and gastrointestinal disorders due to excessive intake. As selenium hypersensitivity, for example, symptoms such as neuropathy, gastrointestinal dysfunction, muscle weakness, hypotension, and the like are known to ultimately cause circulatory collapse and pulmonary edema.

  Therefore, if selenium is dissolved in the waste water, there is a risk of adverse effects on the human body. Therefore, in Japan, selenium water quality standard (0.01 mg-Se / L) was established in 1993. In 1994, a part of the Enforcement Order for the Water Pollution Control Act was revised and the selenium drainage standard (0.1 mg-Se / L) was established.

  In order to comply with the effluent standard value, it is necessary to continuously monitor and manage the selenium concentration in the effluent. Therefore, various methods for quantitatively analyzing the selenium concentration in the effluent are used.

  First, as an official analysis method of selenium in wastewater, absorption spectrometry using 3,3′-diaminobenzidine (DAB) (JIS K0102 67.1), hydride generation-atomic absorption spectrometry (JIS K0102 67.2). ), Hydride generation-ICP emission analysis (JIS K0102 67.3) is used (Non-patent Document 1).

Absorption analysis using DAB is performed by reacting DAB with selenite ion (SeO ₃ ²⁻ ) under acidic conditions in a boiling water bath to form a pierce selenol complex (Chemical Formula 1), and extracting this complex into toluene. Then, the absorption at a wavelength of 420 nm is measured.

Hydride generation-atomic absorption spectrometry and hydride generation-ICP emission analysis methods reduce selenite ions by reacting selenite ions with sodium tetrahydroborate (NaBH ₄ ) in an acidic solution. Hydrogen selenide (H ₂ Se) is generated (Chemical Formula 2), and this is measured by an ICP emission analyzer or atomic absorption analyzer to perform quantitative analysis.

  As a highly sensitive analysis method, a fluorescence analysis method using 2,3-diaminonaphthalene (DAN) as a fluorescent reagent is known (Non-patent Document 2). DAN reacts with selenite ion to form a fluorescent 4,5-benzopiaselenol complex (Chemical Formula 3). Since this complex is weakly luminescent in water, organic solvents such as chloroform, toluene, cyclohexane, etc. Measurement is performed after extraction. This fluorescence analysis method is very sensitive, and it is possible to measure tetravalent selenium at a pg to ng level by concentrating simultaneously with extraction. As a fluorescence analysis method using DAN as a fluorescent reagent, a method in which liquid-liquid extraction is simplified using a surfactant is also known (Non-patent Document 3).

Industrial wastewater test method (JIS K 0102 67), Japan Industrial Water Association, April 20, 1998 C. A. Rarker and L. G. Harvey: “Luminescence of some piazselenols. A new fluorimetric reagent for selenium”, Analyst, 87, 558-565 (1962). J. Pedro, F. Andrade, D. Magni, M. Tudino, A. Bonivardi: “On-line submicellar enhanced fluorometric determination of Se (IV) with 2,3-diaminonaphthalene”, Anal. Chim. Acta, 516, 229 -236 (2004).

  Along with the establishment of selenium drainage standards (0.1mg-Se / L), selenium concentration is monitored on-site as a tool for more appropriate continuous monitoring and management of selenium concentration in wastewater. The need for automatic measuring machines (process monitors) is increasing. In order to realize an automatic measuring machine that monitors the selenium concentration in the field, it has detection sensitivity that can cover the wastewater standard value, easy management of chemicals used, low running cost, measuring instruments and utilities There is an urgent need to establish a method that can perform quantitative analysis of selenium quickly and easily while having a large size and not being expensive. However, the above-described quantitative analysis method of selenium cannot perform quantitative analysis of selenium having all these conditions.

  That is, when the absorption analysis method using DAB is adopted, since the measurement range of the tetravalent selenium concentration is 1.0 to 7.0 mg-Se / L, the drainage standard value of 0.1 mg-Se / L Measurement cannot be performed. Therefore, in order to measure 0.1 mg-Se / L which is the wastewater standard value, co-precipitation of selenite ion contained in the sample for analysis with iron (III) hydroxide results in the formation of tetravalent selenium. A pretreatment for concentration and separation of impurities is required. However, such pretreatment and the treatment of extracting the piazselenol complex with toluene are very complicated. In addition, the DAB aqueous solution deteriorates in about one week, and the DAB itself is expensive, which increases the cost for analyzing tetravalent selenium.

  The hydride generation-atomic absorption analysis method and the hydride generation-ICP emission analysis method require a relatively short measurement time of about 20 minutes and can perform high-sensitivity measurement. Compared with an analysis device such as a photometer, an expensive and large-sized device is required, and utilities such as high-pressure gas and exhaust equipment are required. Therefore, application to a simple measurement device used in on-site analysis is very difficult.

  In addition, since the fluorescence analysis method using DAN has a measurement range of tetravalent selenium concentration of 0.1 to 1 μg-Se / L, it is a highly sensitive quantitative analysis method, but it takes 30 minutes to complex. It takes time and requires an operation for extraction into cyclohexane, which is complicated. In addition, when adopting a method that simplifies liquid-liquid extraction using a surfactant, it is difficult to analyze a sample having turbidity by the fluorescence analysis method, so that the suspension (SS) in the sample for analysis Need to be separated. Moreover, DAN used as a fluorescent reagent is expensive, and the cost for analyzing tetravalent selenium increases.

  Therefore, an object of the present invention is to provide a quantitative analysis method suitable for on-site analysis of tetravalent selenium concentration in waste water.

  Another object of the present invention is to provide a system for carrying out a quantitative analysis method suitable for on-site analysis of tetravalent selenium concentration in waste water.

  The method for quantitative analysis of selenium according to claim 1 for solving such a problem is that at least one of hydrochloric acid and sulfuric acid is added to an analytical sample in which tetravalent selenium is dissolved, so that the normality of the acid is 0. A step of obtaining a sample for acid analysis of 13 to 6.7 N / L, and adding sodium tetrahydroborate at a rate of 5 g / min or less to 1 L of the sample for acid analysis, causing tetravalent selenium and sodium tetrahydroborate to react. A step of generating hydrogen selenide, a step of sucking hydrogen selenide at 10 to 20 mL / min, a step of measuring the sucked hydrogen selenide with a potentiostatic sensor, and obtaining a measured value; And a step of analyzing the tetravalent selenium concentration of the analytical sample based on a calibration curve method, wherein the calibration curve used for the calibration curve method is a tetravalent selenium concentration obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations. Constant It is assumed that was created based on the correlation between the measured value of the position electrolytic sensor.

  The quantitative analysis system for selenium according to claim 5 for solving such a problem is characterized in that at least one of hydrochloric acid and sulfuric acid is added to an analytical sample in which tetravalent selenium is dissolved, and the normality of the acid is determined. A container having an airtight structure in which a sample for acid analysis adjusted to 0.13 to 6.7 N / L, means for adding sodium tetrahydroborate at a rate of 5 g / min or less to 1 L of acid analysis sample, and selenium A constant potential electrolytic sensor that measures hydrogen fluoride and outputs a measurement value; and a supply means that sucks hydrogen selenide generated from the sample for acidic analysis at 10 to 20 mL / min and supplies the hydrogen selenide to the constant potential electrolytic sensor; It has a calibration curve created based on the correlation between the tetravalent selenium concentration obtained in advance from a plurality of standard samples with known tetravalent selenium concentration and the measured value of the potentiostatic sensor, and from the measured value based on the calibration curve It is intended to include an analysis means for analyzing the tetravalent selenium concentration 析用 sample.

  With this configuration, the amount of hydrogen generated per unit time can be suppressed to an amount that does not affect the measured value of hydrogen selenide by a potentiostatic sensor. That is, measurement of hydrogen selenide using a constant potential electrolytic sensor can be performed while sufficiently eliminating the influence of hydrogen.

  Next, in the quantitative analysis method for selenium according to claim 2, at least one of hydrochloric acid and sulfuric acid is added to an analytical sample in which tetravalent selenium is dissolved, and the normality of the acid is 0.13 to 6. A step of obtaining a 7N / L acidic analysis sample, and sodium tetrahydroborate added at 5 to 10 g / min with respect to 1 L of the acidic analysis sample to react tetravalent selenium and sodium tetrahydroborate to hydrogen selenide Generating a hydrogen selenide, adding a carrier gas to the hydrogen selenide at 500 to 700 mL / min, sucking the hydrogen selenide together with the carrier gas at a rate of 400 to 600 mL / min, and determining the sucked hydrogen selenide. It includes a step of obtaining a measurement value by measuring with a potential electrolysis sensor, and a step of analyzing the tetravalent selenium concentration of the sample for analysis by the calibration curve method based on the measurement value, and is used for the calibration curve method Ryosen is assumed to tetravalent selenium concentration is created based on the correlation between the measured value of tetravalent selenium concentration and the constant potential electrolysis sensor obtained in advance from the known multiple standard samples.

  Further, in the quantitative analysis system for selenium according to claim 6, at least one of hydrochloric acid and sulfuric acid is added to the analytical sample in which tetravalent selenium is dissolved, and the normality of the acid is 0.13 to 6. A container having a sealed structure in which a sample for acid analysis adjusted to 7 N / L is placed, a means for adding sodium tetrahydroborate at 5 to 10 g / min with respect to 1 L of the sample for acid analysis, and a carrier gas of 500 to 500 A means for supplying at 700 mL / min, a potentiostatic sensor that measures hydrogen selenide and outputs the measured value, and hydrogen selenide generated from the sample for acidic analysis is sucked together with a carrier gas at 400 to 600 mL / min. Based on the correlation between the supply means for supplying to the potentiostatic sensor and the tetravalent selenium concentration obtained from a plurality of standard samples with known tetravalent selenium concentrations and the measured value of the potentiostatic sensor It is intended to include an analysis means for analyzing the tetravalent selenium concentration of the sample for analysis from the measured value based on a calibration curve which has a calibration curve prepared by have.

  As described above, by using the carrier gas in combination, the quantitative analysis accuracy can be improved, and it is possible to perform the quantitative analysis up to a lower concentration region than in the case where the carrier gas is not used together.

  Here, it is preferable to add nitric acid to an acidic analysis sample to which sulfuric acid is added as an acid, and to heat the sample to generate white smoke. Desulfurization effluent discharged from coal-fired power plants, etc. contains substances that interfere with the measurement of hydrogen selenide, such as organic matter and iodide ions. By this treatment, organic matter and iodide Ions can be removed and at the same time a sample for acidic analysis can be obtained.

  Furthermore, nitric acid is added to an acid analysis sample to which sulfuric acid has been added as an acid, and this is heated to produce sulfuric acid white smoke. Then, hydrochloric acid is added as an acid to the sulfuric acid and hydrochloric acid to regulate the acid. The degree is preferably 4.0 to 6.7 N / L. In this case, organic substances and iodide ions can be removed, and at the same time, a sample for acidic analysis can be obtained. In addition, the quantitative accuracy of hydrogen selenide using a potentiostatic sensor can be increased.

  According to the quantitative analysis method for selenium according to claim 1 and the quantitative analysis system according to claim 5, the amount of hydrogen generated per unit time does not affect the measured value of hydrogen selenide by a potentiostatic sensor. The amount can be suppressed. That is, measurement of hydrogen selenide using a potentiostatic sensor can be performed while sufficiently eliminating the influence of hydrogen, so that the tetravalent selenium concentration of the analytical sample can be accurately quantitatively analyzed. In addition, quantitative analysis can be performed easily and quickly without performing complicated pretreatment and extraction processing as in the conventional quantitative analysis method for selenium.

  In addition, since most of the hydrogen selenide used for the measurement is dissolved as selenite ion in the electrolyte of the potentiostatic sensor, the tetravalent selenium dissolved in the analytical sample must be recovered and reused. Is possible.

  According to the quantitative analysis method for selenium according to claim 2 and the quantitative analysis system according to claim 6, the quantitative analysis accuracy can be improved, and quantitative analysis is performed even in a lower concentration region than in the case where no carrier gas is used in combination. Can be performed.

  According to the quantitative analysis method for selenium according to claim 3 and the quantitative analysis system according to claim 7, when the sample for analysis contains a substance that interferes with the measurement of hydrogen selenide, such as an organic substance or iodide ion. Even so, it is possible to remove organic substances and iodide ions and obtain an accurate measurement value. Moreover, there is an advantage that a sample for acidic analysis can be obtained simultaneously with the removal of organic substances and iodide ions.

  According to the quantitative analysis method for selenium according to claim 4 and the quantitative analysis system according to claim 8, when the sample for analysis contains a substance that interferes with the measurement of hydrogen selenide, such as an organic substance or iodide ion. Even so, it is possible to remove organic substances and iodide ions and obtain an accurate measurement value. Moreover, there is an advantage that a sample for acidic analysis can be obtained simultaneously with the removal of organic substances and iodide ions. Furthermore, since the measured value (signal intensity) of hydrogen selenide by a potentiostatic sensor can be sufficiently increased, more accurate and highly accurate quantitative analysis can be performed.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

(First embodiment)
In the method for quantitative analysis of selenium according to the first embodiment of the present invention, at least one of hydrochloric acid and sulfuric acid is added to an analytical sample in which tetravalent selenium is dissolved, and the normality of the acid is 0.13 to 0.13. A step of obtaining a sample for acid analysis of 6.7 N / L, and sodium tetrahydroborate is added at a rate of 5 g / min or less to 1 L of acid analysis sample, and tetravalent selenium is reacted with sodium tetrahydroborate to selenize. A step of generating hydrogen, a step of sucking hydrogen selenide at 10 to 20 mL / min, a step of measuring the sucked hydrogen selenide with a potentiostatic sensor and obtaining a measured value, and based on the measured value And a step of analyzing the tetravalent selenium concentration of the analytical sample by a calibration curve method. The calibration curve used for the calibration curve method is a tetravalent selenium concentration and a constant potential obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations Electrolytic type Based on the correlation of the measured values of the capacitors are assumed to have been created.

  An example of a system for carrying out the quantitative analysis method of selenium of the present invention is shown in FIG. This system 1 is an acid analysis in which at least one of hydrochloric acid and sulfuric acid is added to an analytical sample in which tetravalent selenium is dissolved, and the normality of the acid is adjusted to 0.13 to 6.7 N / L. A container 2 having a sealed structure for containing the sample 2a for use, means 3 (hereinafter referred to as addition means 3) for adding sodium tetrahydroborate 3a at 5 g / min or less to 1 L of the sample for acidic analysis, hydrogen selenide A controlled-potential electrolytic sensor 4 that measures and outputs a measured value; a supply means that sucks hydrogen selenide generated from the acidic analysis sample 2a at 10 to 20 mL / min and supplies the hydrogen selenide to the controlled-potential electrolytic sensor 4; A calibration curve created based on the correlation between the tetravalent selenium concentration obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations and the measured value of the potentiostatic sensor 4 is stored, and measured based on the calibration curve. Sample for analysis from values It is intended to include analysis means 5 for analyzing the tetravalent selenium concentration. In this embodiment, hydrogen selenide generated in the container 2 by the constant potential electrolytic sensor 4 is sucked through the tube body 9. That is, the constant potential electrolytic sensor 4 itself also serves as a supply means.

  Further, in the quantitative analysis system 1 shown in FIG. 1, the hydrogen selenide that has not dissolved in the electrolytic solution of the potentiostatic sensor 4 is brought into contact with the copper sulfate solution 6a and recovered (hereinafter referred to as the recovery means 6). ).

The addition means 3 is connected to the container 2 via a tube 8, and the constant potential electrolytic sensor 4 is connected via a tube 9. The parts other than the connection part are sealed. Therefore, leakage of hydrogen selenide (H ₂ Se) generated by adding sodium tetrahydroborate 3a to the sample 2a for acidic analysis is prevented.

  Examples of the material constituting the container 2 include, but are not limited to, acid-resistant materials such as glass and fluororesin.

Samples for analysis include all types of samples in which tetravalent selenium may be dissolved. Examples thereof include, but are not limited to, wastewater discharged from factories and coal-fired power generation facilities and coal ash disposal site elution water. The tetravalent selenium means selenium dissolved in water and existing in the form of selenite ion (SeO ₃ ²⁻ ).

  The acid analysis sample 2a is obtained by adding at least one of hydrochloric acid and sulfuric acid to the analysis sample. That is, it can be obtained by adding hydrochloric acid alone, sulfuric acid alone, or a mixture of hydrochloric acid and sulfuric acid. In order to increase the signal intensity at the time of measurement by the constant potential electrolytic sensor 4, it is preferable to use hydrochloric acid.

  The specified value of the acid of the acid analysis sample 2a is defined by at least one of hydrochloric acid and sulfuric acid added to the analysis sample, and may be 0.13 to 6.7 N / L. It is preferably 6.7 N / L, more preferably 1.3 to 6.7 N / L, still more preferably 2.0 to 6.7 N / L, and more preferably 4.0 to 6.7 N. / L is most preferable. If the specified value of the acid exceeds 6.7 N / L, the tetravalent selenium tends to remain unreacted in the acidic analysis sample after completion of the quantitative analysis, and an accurate quantitative analysis result may not be obtained. The amount of acid used is also increased, which is not preferable. When the specified value of the acid is less than 0.13 N / L, the signal intensity at the time of measurement by the potentiostatic sensor 4 is not sufficient. As the specified value of acid approaches the range of 4.0 to 6.7 N / L, the signal intensity at the time of measurement by the potentiostatic sensor 4 becomes sufficient. Further, there is no possibility that tetravalent selenium remains unreacted in the acidic analysis sample after completion of the quantitative analysis.

  The concentration and amount of the acid to be added are, for example, 0.2 to 10 mol / L, preferably 1.0 to 10 mol / L, more preferably 2.10 when the sample for analysis is neutral and the volume is 5 mL. Hydrochloric acid aqueous solution having a concentration of 0 to 10 mol / L, more preferably 3.0 to 10 mol / L, most preferably 6.0 to 10 mol / L (0.2 to 10 N / L, preferably 1.0 to 10 N / L) More preferably, 10 mL of a hydrochloric acid aqueous solution having a concentration of 2.0 to 10 N / L, more preferably 3.0 to 10 N / L, and most preferably 6.0 to 10 N / L may be added.

  Here, wastewater discharged from factories and coal-fired power generation facilities and elution water from coal ash disposal sites contain substances that interfere with the measurement of hydrogen selenide, such as organic compounds and iodide ions, using the potentiostatic sensor 4. May be included. Therefore, it is preferable to pre-process the analysis sample according to the JIS method (JIS-K0102.67.3.). This pretreatment is a technique in which sulfuric acid and nitric acid are added to an analytical sample and heated to generate white fuming sulfuric acid. Thus, it is known that the organic compound can be removed, but the inventors of the present application have found that this method can also remove iodide ions at the same time. Moreover, since sulfuric acid is added to the analysis sample, it is preferable that the acid analysis sample be prepared at the same time if the predetermined value of the acid defined by the sulfuric acid is 0.13 N / L or more. In addition, when conforming to the JIS method, the default value of the acid by sulfuric acid of the analysis sample is 0.34 N / L. That is, a sample for acid analysis can be obtained simply by adopting a method according to the JIS method. Of course, the pretreatment may be performed by further increasing the concentration of sulfuric acid. Since nitric acid does not have the effect of enhancing the action of sodium tetrahydroborate as a reducing agent, the default value for the acid in the sample for acidic analysis needs to be defined by at least one of sulfuric acid and hydrochloric acid. In addition, when conforming to the JIS method, the amount of nitric acid added to the analytical sample is 2 mL of concentrated nitric acid (13.5 N / L) with respect to 50 mL of the sample.

  Furthermore, at least one of sulfuric acid and hydrochloric acid, preferably hydrochloric acid, is added to the acidic analysis sample obtained by the pretreatment according to the JIS method, and the default value of the acid is set to 4.0 to 6.7 N / L. It is preferable that In this case, interfering substances when measuring hydrogen selenide such as organic compounds and iodide ions with the potentiostatic sensor 4 can be removed, and the signal intensity when measuring with the potentiostatic sensor 4 is sufficient. Can be. Further, there is no possibility that tetravalent selenium remains unreacted in the acidic analysis sample after completion of the quantitative analysis.

  As the nitric acid addition means and hydrochloric acid addition means, those having the same mechanism as the addition means 3 described later may be used. Further, as the heating device, since the pretreatment by the JIS method needs to be performed at 170 ° C., a heater or the like that can heat the acidic analysis sample to about 170 ° C. may be used.

  From addition means 3, sodium tetrahydroborate 3a is added at 5 g / min or less to 1 L of acidic analysis sample. Sodium tetrahydroborate 3a and sample 2a for acid analysis react with selenite ions according to the chemical reaction formula shown in Chemical formula 4 to generate hydrogen selenide.

  Sodium tetrahydroborate 3a is highly hygroscopic and gradually deteriorates by absorbing moisture in the air. Therefore, sodium tetrahydroborate 3a is used by dissolving it in a solvent capable of stably maintaining it. As a solvent for dissolving sodium tetrahydroborate, it is preferable to use a weakly alkaline solvent. If an acidic solvent is used, sodium tetrahydroborate may be deteriorated. Even when a neutral solvent is used, sodium tetrahydroborate may be gradually deteriorated. When a strongly alkaline solvent is used, the pH tends to fluctuate to the alkali side when added to the acidic analysis sample 2a, and its function as a reducing agent for sodium tetrahydroborate is reduced and dissolved in the analysis sample. There is a risk that the selenite ion that is present cannot be sufficiently reduced. That is, a solvent that does not degrade sodium tetrahydroborate and does not lower the function of sodium tetrahydroborate as a reducing agent by changing the pH to the alkali side when added to the sample for acidic analysis 2a. Use it. For example, a 0.1 mol / L sodium hydroxide solution may be mentioned, but is not limited thereto.

  In addition, sodium tetrahydroborate is a compound widely used as a reducing agent, and is inexpensive and easily available. Further, by adding ethylenediaminetetraacetic acid, it can be dissolved in a 0.1 mol / L sodium hydroxide solution and stably stored for 30 days (AD Idowu, PK Dasgupta, Z. Genfa, and K. Toda: “ A Gas-Phase Chemiluminescence-Based Analyzer for Waterborne Arsenic ”, Anal. Chem., 78, 7088-7097 (2006)). That is, it is a reagent having both ease of use and stability, and is very suitable as a reagent used for on-site analysis.

  As the adding means 3, one that can control the addition rate of a solution in which sodium tetrahydroborate 3a is dissolved is appropriately used. For example, one that can control the addition rate by adjusting the opening of the cock (valve), such as a separatory funnel or burette, or one that can be added at a constant rate only when the valve is open Can also be used. Further, by using a highly controllable device such as a peristaltic pump as the adding means 3, more accurate quantitative analysis is possible.

  The addition rate of sodium tetrahydroborate 3a added to the acidic analysis sample 2a may be 5 g / min or less with respect to 1 L of the acidic analysis sample, but is preferably 4 g / min or less. In this case, selenite ions dissolved in the analytical sample can be reduced to hydrogen selenide while suppressing the generation of hydrogen per unit time. That is, it is possible to suppress the hydrogen generation amount without interfering with the measurement of hydrogen selenide by the constant potential electrolytic sensor 4. If sodium tetrahydroborate 3a is added at a rate exceeding 5 g / min with respect to 1 L of the acidic analysis sample, hydrogen may be generated in an amount that affects the measurement of hydrogen selenide.

  Here, the lower limit value of the addition rate of sodium tetrahydroborate means a measured value per unit time of hydrogen selenide measured by a potentiostatic sensor (the signal intensity output from the potentiostatic sensor). Hereinafter, the measured value may be referred to as signal intensity), and a value that sufficiently secures the rapidity of quantitative analysis is appropriately selected. For example, it may be 0.01 g / min or more with respect to 1 L of the acidic analysis sample, but is preferably 0.1 g / min or more, and more preferably 0.2 g / min or more.

  In order to maximize the speed of quantitative analysis, it is preferable to increase the addition rate without generating an amount of hydrogen that affects the measurement of hydrogen selenide. That is, it is preferably 1 g / min or more, more preferably 2 g / min or more, and further preferably 3 g / min or more with respect to 1 L of the acidic analysis sample.

  The addition rate of sodium tetrahydroborate 3a is appropriately controlled by the concentration of sodium tetrahydroborate in the solution in which sodium tetrahydroborate 3a is dissolved and the addition rate of the sample for acidic analysis 2a.

  That is, if the concentration of the sodium tetrahydroborate solution is increased and added to the acidic analysis sample 2a, the addition rate of the sodium tetrahydroborate 3a to the acidic analysis sample 1L can be increased. Further, if the addition rate of the sodium tetrahydroborate solution to the acidic analysis sample 2a is increased, the addition rate of the sodium tetrahydroborate 3a to the acidic analysis sample 1L can be increased. Conversely, if the concentration of the sodium tetrahydroborate solution is lowered and added to the acidic analysis sample 2a, the rate of addition of the sodium tetrahydroborate 3a to the acidic analysis sample 1L can be reduced. Further, if the addition rate of the sodium tetrahydroborate solution to the acidic analysis sample 2a is reduced, the addition rate of the sodium tetrahydroborate 3a to the acidic analysis sample 1L can be reduced. Therefore, the addition rate of sodium tetrahydroborate 3a may be controlled by appropriately controlling the concentration of the sodium tetrahydroborate solution and the addition rate to the acidic analysis sample 2a.

  For example, if it is a sodium tetrahydroborate solution having a concentration of more than 3 g / L and not more than 5 g / L, the concentration is preferably 5 to 8 mL / min with respect to 15 mL of the sample for acidic analysis. If it is a sodium tetrahydroborate solution with a concentration of 1 g / L to 3 g / L, it is preferably 5 to 35 mL / min, more preferably 10 to 15 mL / min, with respect to 15 mL of the sample for acidic analysis. In this case, generation of hydrogen per unit time is suppressed and measurement of hydrogen selenide is not hindered. In addition, sufficient signal intensity of hydrogen selenide and rapidness of quantitative analysis are ensured.

As for the amount of sodium tetrahydroborate 3a added to the acid analysis sample 2a, an amount that is more than the amount capable of reducing the total amount of tetravalent selenium considered to be dissolved in the analysis sample to hydrogen selenide is appropriately selected. The As shown in Chemical Formula 4, in order to reduce 1 mol of H ₂ SeO ₃ (SeO ₃ ²⁻ ) to generate hydrogen selenide, _3/4 mol of NaBH ₄ (BH ₄ ⁻ ) is required. Therefore, a minimum of 0.38 mg NaBH ₄ is required for 1 mg of tetravalent selenium. Here, in order to reliably reduce the total amount of tetravalent selenium dissolved in the analytical sample to hydrogen selenide, an excess amount relative to the total amount of tetravalent selenium considered to be contained in the analytical sample. It is preferred to add an amount of sodium tetrahydroborate. That is, when it is assumed that the tetravalent selenium concentration of the analytical sample is 1 mg / L or less, it is preferable to add 0.38 mg to 6.7 g of sodium tetrahydroborate to 1 L of the analytical sample, It is more preferable to set it as 3.8 mg-3.4 g, and it is still more preferable to set it as 38 mg-2.0 g. Even if an amount of sodium tetrahydroborate exceeding 6.7 g is added, it does not affect the measurement of hydrogen selenide, but it is useless because it does not participate in the hydrogen selenide generation reaction. For example, according to experiments by the present inventors, an analytical sample of at least 0.7 mg / Se-L is obtained by adding 10 mL of 3 g / L sodium tetrahydroborate solution to 15 mL of acidic analytical sample 2a. Then, it has been confirmed by experiments by the present inventors that 90% or more of tetravalent selenium dissolved in the sample for analysis can be reduced to hydrogen selenide within 10 minutes. However, it is not limited to this condition.

  Further, it is preferable to continue stirring the acidic analysis sample 2a from the start of the addition of the sodium tetrahydroborate 3a to the acidic analysis sample 2a until the measurement by the constant potential electrolytic sensor 4 is completed. If the stirring is not sufficiently performed, the sodium tetrahydroborate 3a added to the acidic analysis sample 2a does not sufficiently diffuse and easily reacts nonuniformly with the acidic analysis sample 2a. There is a possibility that the signal intensity of hydrogen fluoride may be reduced.

  Hydrogen selenide generated by adding sodium tetrahydroborate 3a to the acidic analysis sample 2a is sucked by the constant potential electrolytic sensor 4 and measured as needed, and a measured value is output.

The measurement principle of hydrogen selenide by the constant potential electrolytic sensor 4 is shown in FIG. Hydrogen selenide is diffused and absorbed into the electrolyte through the gas permeable membrane. The hydrogen selenide diffused and absorbed in the electrolytic solution generates an electric current when electrolyzed at a constant potential in the electrolytic solution. The constant potential electrolytic sensor 4 measures the current at this time by amplifying it with an amplifier 14. During electrolysis, an oxidation reaction occurs at the working electrode 11 (chemical reaction formula A), and a reduction reaction proceeds at the counter electrode 13 (chemical reaction formula B). The current flowing through the working electrode 11 and the counter electrode 13 is proportional to the hydrogen selenide concentration. The verification electrode 12 is connected to a verification electrode reference power source 12a, and performs electrolysis by regulating the potential of the working electrode with respect to the verification electrode.
(Chemical reaction formula A) Working electrode: H ₂ Se + 3H ₂ O → H ₂ SeO ₃ + 6H ⁺ + 6e ⁻
(Chemical reaction formula B) Counter electrode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O

  As shown in the chemical reaction formula A, hydrogen selenide sucked into the constant potential electrolytic sensor 4 and used for measurement is taken into the electrolytic solution by a reaction on the surface of the working electrode 11 of the constant potential electrolytic sensor 4. As a result, most of the tetravalent selenium dissolved in the sample for analysis is recovered in the electrolytic solution. Therefore, selenium can be recovered from this electrolytic solution and reused. That is, according to the present invention, it is possible to achieve both the quantitative analysis of tetravalent selenium and the recovery of tetravalent selenium contained in the analytical sample.

  The constant potential electrolysis sensor 4 in the present embodiment includes XPS-7 manufactured by New Cosmos Electric, which is a semiconductor material gas detector marketed as a leak gas detector (dedicated hydrogen selenide sensor unit XDS-7Se). It is not limited to this, What is functionally similar to this can be used.

  Here, in order to measure the hydrogen selenide generated in the container 2 with the constant potential electrolytic sensor 4, it is necessary to provide a supply means for supplying the hydrogen selenide to the constant potential electrolytic sensor 4. New Cosmos Electric XPS-7 has a gas suction function, and by using this, hydrogen selenide generated in the container 2 is sucked. That is, the gas suction function of the constant potential electrolytic sensor 4 functions as supply means for supplying hydrogen selenide generated in the container 2 to the constant potential electrolytic sensor 4. The XPS-7 manufactured by New Cosmos Electric has a gas suction function of 15 mL / min, and the analysis conditions are derived based on the suction speed. It is considered that even 20 mL / min can be applied.

  Next, in the analysis means 5, the measurement value output from the constant potential electrolytic sensor 4 is input, and the tetravalent selenium concentration of the analysis sample is analyzed by the calibration curve method based on the measurement value.

  The calibration curve used in the calibration curve method is a correlation between the tetravalent selenium concentration obtained beforehand from a plurality of standard samples with known tetravalent selenium concentrations and the measured value of the potentiostatic sensor 4 (hydrogen selenide signal intensity). It was created based on. More specifically, a step of adding an acid to each of a plurality of standard samples having a known tetravalent selenium concentration to obtain an acid analysis sample, and 5 g / min or less with respect to 1 L of the acid analysis sample Adding sodium tetrahydroborate, reacting tetravalent selenium with sodium tetrahydroborate to generate hydrogen selenide, and measuring hydrogen selenide with a potentiostatic sensor to obtain measured values From the relationship between the obtained measured value (the signal intensity of hydrogen selenide) and the tetravalent selenium concentration, it can be obtained by fitting by a known method such as the least square method.

  The analysis of the tetravalent selenium concentration of the sample for analysis by the calibration curve method is realized, for example, by executing it on a computer. That is, for example, a computer is used as the analysis means 5.

  FIG. 3 shows the overall configuration of the computer 15 as the analysis means 5. The computer 15 includes a control unit 16, a storage unit 17, an input unit 18, a display unit 19, and a memory 20, which are connected to each other by a signal line 21 such as a bus. In addition, a data server 22 is connected to the computer 10 via a communication line or the like, and transmission / reception (input / output) of signals such as data and control commands is performed via the communication line.

  The control unit 16 uses the calibration curve coefficients (slope and intercept) stored in the storage unit 17 to calculate the tetravalent selenium concentration of the analytical sample from the measured value (hydrogen selenide signal intensity) obtained from the analytical sample. It performs operations related to analysis, and is, for example, a CPU. The storage unit 17 is a device capable of storing at least data and programs, and is, for example, a hard disk. The input unit 18 is an interface for giving at least an operator command to the CPU, and is, for example, a keyboard. The display unit 19 displays characters, graphics, and the like under the control of the control unit 16 and is, for example, a display. The memory 20 becomes a memory space that is a work area when the control unit 16 executes various controls and calculations. The data server 22 is a server capable of storing at least data. The measurement value (hydrogen selenide signal intensity) output by the potentiostatic sensor 4 is temporarily stored in the data server 22 and then transmitted to the computer 15. Note that the measurement value (the signal intensity of hydrogen selenide) output from the potentiostatic sensor 4 can be directly transmitted to the computer 15 without providing the data server 22.

  Here, in the constant potential electrolytic sensor 4, the measured signal intensity is output as a signal profile of 0 to 10 minutes, for example, as shown in FIG. At the beginning of the measurement, since the air in the container 2 is sucked by the constant potential electrolytic sensor 4, the signal intensity is zero. The measurement value for creating the calibration curve and the measurement value of the sample for analysis may be the peak intensity of the signal profile or the area value of the signal profile. In any case, it has been confirmed by experiments by the inventors of the present application that extremely high linearity is obtained when the tetravalent selenium concentration is in the range of 0.01 to 0.7 mg-Se / L. That is, in the range of 0.01 to 0.7 mg-Se / L, the tetravalent selenium concentration of the analytical sample can be quantified with extremely high accuracy.

  Most of the hydrogen selenide generated in the container 2 is diffused and absorbed through the gas permeable membrane into the electrolyte, but some hydrogen selenide does not pass through the gas permeable membrane and is diffused and absorbed into the electrolyte. Without being discharged from the constant potential electrolytic sensor 4 in some cases. Therefore, the recovery means 6 recovers such hydrogen selenide by contacting the copper sulfate solution 6a. The hydrogen selenide that has contacted the copper sulfate solution 6a is absorbed by the copper sulfate solution 6a and recovered. Therefore, hydrogen selenide is not scattered in the environment, but also has an excellent advantage that industrially useful selenium can be reused. The hydrogen selenide absorbed in the copper sulfate solution is fixed as a precipitate and recovered. Here, the solution used for the recovery means is not limited to the copper sulfate solution, but includes heavy metal salts such as copper, zinc, silver, mercury, cadmium and iron, for example, nitrate, nitrate, in addition to sulfate, nitrate and halide. And strong acid solutions such as hydrochloric acid (JP-A-11-50294, ACF Gomes, AA Menegario, DC Pellegrinotti, MF Gine, VFN Filho: “A hydride generation flow system for determination of arsenic and selenium by total reflection X- ray fluorescence spectrometry ", spctrochim. Acta B, 59,1481-1484 (2004)), but is not limited thereto.

(Second embodiment)
An example of the selenium quantitative analysis system of the present invention according to the second embodiment is shown in FIG. This selenium quantitative analysis system 1 ′ is an acid analysis sample 2 a in which acid is added to an analysis sample in which tetravalent selenium is dissolved, and the acid concentration is adjusted to 0.13 to 6.7 N / L. A container 2 having a sealed structure, a means 3 for adding sodium tetrahydroborate 3a at 5 to 10 g / min or less with respect to 1 L of the sample for acidic analysis (hereinafter referred to as addition means 3), and 500 to 700 mL of carrier gas. Supply means (hereinafter referred to as carrier gas supply means 7), a constant potential electrolytic sensor 4 that measures hydrogen selenide and outputs the measured value, and hydrogen selenide generated from the sample for acidic analysis 2a Is supplied at a rate of 400 to 600 mL / min together with a carrier gas and supplied to the constant potential electrolysis sensor 4, and a tetravalent selenium concentration and a constant potential obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations. A calibration curve created on the basis of the correlation with the measurement value of the electrolytic sensor 4 is stored, and includes analysis means 5 for analyzing the tetravalent selenium concentration of the analytical sample from the measurement value based on the calibration curve. In this embodiment, hydrogen selenide generated in the container 2 by the constant potential electrolytic sensor 4 is sucked through the tube body 9. That is, the constant potential electrolytic sensor 4 itself also serves as a supply means.

The quantitative analysis system 1 ′ shown in FIG. 24 further includes means 6 for recovering hydrogen selenide that has not dissolved in the electrolytic solution of the potentiostatic sensor 4 by bringing it into contact with the copper sulfate solution 6a. Furthermore, the addition means 3 is connected to the container 2 via a tube 8, the constant potential electrolysis sensor 4 is connected via a tube 9, and the carrier gas supply means 7 is connected via a tube 10. ing. The parts other than the connection part are sealed. Therefore, leakage of hydrogen selenide (H ₂ Se) generated by adding sodium tetrahydroborate 3a to the sample 2a for acidic analysis is prevented.

  The selenium quantitative analysis system according to the second embodiment is different from the selenium quantitative analysis system according to the first embodiment in that a carrier gas is supplied to a container having a sealed structure in which a sample for acidic analysis is placed. . As the carrier gas is supplied, the analysis conditions differ from the selenium quantitative analysis system according to the first embodiment. Hereinafter, differences between the selenium quantitative analysis system of the second embodiment and the selenium quantitative analysis system of the first embodiment will be described in detail. The configuration other than the differences described below is common to the selenium quantitative analysis system of the first embodiment, and the description thereof is omitted.

  The addition rate of sodium tetrahydroborate 3a added to the acidic analysis sample 2a is preferably 5 to 10 g / min or less with respect to 1 L of the acidic analysis sample. In this case, selenite ions dissolved in the analytical sample can be reduced to hydrogen selenide while suppressing the generation of hydrogen per unit time. That is, it is possible to suppress the hydrogen generation amount without interfering with the measurement of hydrogen selenide by the constant potential electrolytic sensor 4. If sodium tetrahydroborate 3a is added at a rate exceeding 10 g / min with respect to 1 L of the acidic analysis sample, hydrogen may be generated in an amount that affects the measurement of hydrogen selenide.

  Moreover, about the lower limit of the addition rate of sodium tetrahydroborate, the measured value per unit time of hydrogen selenide measured by a constant potential electrolytic sensor (the signal intensity output from the constant potential electrolytic sensor is meant. The measured value may be referred to as signal intensity.), And a value that ensures sufficient quantitative analysis and speed of quantitative analysis is appropriately selected. For example, it is preferable to set it as 5 g / min or more with respect to 1 L of acidic analysis samples, and it is more preferable to set it as 6 g / min.

  Here, the addition of sodium tetrahydroborate will be specifically described with an example. If the sodium tetrahydroborate solution has a concentration of 3 g / L, it is 25 to 50 mL / min with respect to 15 mL of the sample for acidic analysis. Preferably, it is more preferably 30 mL / min. In this case, generation of hydrogen per unit time is suppressed and measurement of hydrogen selenide is not hindered. In addition, sufficient signal intensity of hydrogen selenide and rapidness of quantitative analysis are ensured.

  A carrier gas is supplied to the container 2 by a carrier gas supply means 7.

  As the carrier gas, not only an inert gas such as nitrogen or argon, but also air can be used. Thus, by using air as a carrier gas, it is possible to supply the carrier gas by sending air from the atmosphere to the container 2 during field analysis, which is very convenient.

  The carrier gas supply means 7 is not particularly limited as long as the supply amount of the carrier gas to the container 2 can be controlled. For example, the carrier gas supplied in the cylinder is supplied via the mass flow controller. Alternatively, a predetermined flow rate of air may be supplied by a pump or the like.

  The supply rate of the carrier gas is preferably 500 to 700 mL / min or more. In this case, the upper limit of the quantitative analysis of selenium can be increased.

  Here, the upper limit value of the carrier gas supply rate is preferably set to a value that does not greatly exceed the gas suction capability of the constant potential electrolytic sensor 4. If the gas suction capability of the constant potential electrolytic sensor 4 is greatly exceeded, the gas suction function of the constant potential electrolytic sensor 4 is burdened, and measurement may not be possible. Therefore, the supply rate of the carrier gas is preferably 500 to 700 mL / min, and more preferably a supply rate substantially equal to the gas suction capability of the potentiostatic sensor 4. For example, if the gas suction capability of the potentiostatic sensor 4 is 500 mL / min, the carrier gas supply rate is preferably close to 500 mL / min.

  Hydrogen selenide generated by adding sodium tetrahydroborate 3a to the sample 2a for acid analysis is sucked by the potentiostatic sensor 4 together with the carrier gas supplied by the carrier gas supply means 7, and is measured as needed. Is output.

  As the constant potential electrolytic sensor 4 in this embodiment, PS-7 (dedicated hydrogen selenide sensor unit CDS-7) manufactured by New Cosmos Electric, which is a semiconductor material gas detector marketed as a leak gas detector, can be cited. It is not limited to this, What is functionally similar to this can be used.

  Here, the new Cosmos Electric PS-7 also has a gas suction function, and the hydrogen selenide generated in the container 2 is sucked using this. That is, the gas suction function of the constant potential electrolytic sensor 4 functions as supply means for supplying hydrogen selenide generated in the container 2 to the constant potential electrolytic sensor 4. The gas suction capability of PS-7 manufactured by New Cosmos Electric is 500 mL / min, and the above analysis conditions are derived based on this suction speed. It is considered that even 600 mL / min can be applied.

  As described above, according to the selenium quantitative analysis system of the second embodiment, the accuracy of the selenium quantitative analysis can be increased by using the carrier gas. In addition, it is possible to perform quantitative analysis of selenium at a very low concentration as compared with the case where no carrier gas is used.

  Furthermore, in the new Cosmos Electric XPS-7 cited as the constant potential electrolytic sensor 4 in the first embodiment, data acquisition is performed digitally, data acquisition is performed at intervals of 10 seconds, and within 10 seconds. Is obtained as the measured value, and the resolution with respect to full scale is 1.25%. On the other hand, with the new Cosmos Electric PS-7, data acquisition is performed digitally, data acquisition is performed at 0.1 second intervals, and the resolution with respect to full scale is 0.4%. Thus, the quantitative analysis accuracy of selenium can be improved by using an analog method and improving the data acquisition interval and resolution.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in this embodiment, an acid is added to an analytical sample in which tetravalent selenium is dissolved, and a predetermined value of the acid is adjusted in advance, and then placed in the container 2. It is also possible to separately provide an adding means for adding the acid into the container 2 and adjust the default value of the acid in the container 2.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Experiments were performed using the experimental apparatus shown in FIG. In view of meeting the needs for on-site analysis, all experiments were conducted under normal temperature and pressure. Therefore, the conditions obtained from this experimental result can be applied under normal temperature and pressure.

  A branched Erlenmeyer flask was used as the container 2, and an acid analysis sample 2a, which was adjusted to pH by adding an acid to the analysis sample, was placed. A separatory funnel was used as the adding means 3, the tip 3b of the separatory funnel was passed through a rubber stopper, and the separatory funnel was connected to the branch conical flask by fitting the rubber stopper into the branch. The branch Erlenmeyer flask and the controlled potential electrolytic sensor 4 are formed by passing the tube 9 through a rubber stopper, fitting the rubber stopper into the opening of the branch Erlenmeyer flask, and connecting one end of the tube 9 to the constant potential electrolytic sensor 4. And hydrogen selenide generated in the branched Erlenmeyer flask can be sent to the potentiostatic sensor 4.

  In addition, a magnetic stirrer 26 (8φ, length 30 mm) was placed in the Erlenmeyer flask 2 with a branch, and the rotational speed of the magnetic stirrer 26 could be controlled by the stirring device 25.

In this embodiment, the constant potential electrolytic sensor 4 uses a semiconductor material gas detector (XPS-7) manufactured by New Cosmos Electric Co., Ltd., and XDS-7Se, which is a dedicated sensor unit for hydrogen selenide (H ₂ Se). It was. The gas suction rate of this device is 15 mL / min. The measured value is displayed and recorded as a signal intensity corresponding to the hydrogen selenide concentration after the current value is AD converted in the constant potential electrolytic sensor 4. XDS-7Se has been calibrated at the time of shipment, and the indication accuracy in hydrogen selenide measurement is within 10%. Further, the data acquisition interval (sampling interval) of the signal intensity of hydrogen selenide is an interval of 10 seconds, the signal intensity interval (plot interval) is an interval of 1.25 ppb, and the decimal part is rounded down. The selenium concentration was calculated based on the peak intensity of the signal profile or the area value of the signal profile. The area value was calculated using spreadsheet software Origin (registered trademark).

  The selenite ion dissolved in the analytical sample is reduced and vaporized by adding a sodium tetrahydroborate solution to the acidic analytical sample 2 a placed in the container 2. Here, in this embodiment, the opening 3c of the separatory funnel 3 is opened without being fitted with a lid, so that the selenium generated in the container 2 after the addition of the sodium tetrahydroborate solution is completed. Most of the hydrogen fluoride gas is sent to the constant potential electrolytic sensor 4 by the air vented from the separatory funnel 3. The hydrogen selenide after the measurement was absorbed by the copper sulfate solution 6a and detoxified.

  First, using a selenite standard solution sample in which 0.1 mg-Se / L tetravalent selenium, which is the wastewater standard value, is dissolved, examines whether hydrogen selenide can be measured with a potentiostatic sensor. did.

  10 mL of 5 g / L sodium tetrahydroborate solution (addition rate) to a mixed solution (sample for acidic analysis) of 5 mL of 0.1 mg-Se / L selenite ion aqueous solution and 10 mL of hydrochloric acid aqueous solution (6 mol / L, 1 + 1) : 10 mL to 15 mL / min), and immediately after that, the signal intensity value was measured continuously for 10 minutes with a constant potential electrolytic sensor.

  On the other hand, as a comparative experiment, 10 mL of 5 g / L sodium tetrahydroborate solution (addition rate: 10 mL to 15 mL / mL) was added to a mixed solution (acid sample) of 5.0 mL distilled water and 10 mL hydrochloric acid aqueous solution (6 mol / L, 1 + 1). And the signal intensity value was continuously measured for 10 minutes by a constant potential electrolytic sensor, and the signal intensity value of a sample (blank) in which tetravalent selenium was not dissolved was examined.

  The sodium tetrahydroborate solution was prepared by diluting with a 0.1 mol / L sodium hydroxide aqueous solution. During the experiment, the rotation speed of the magnetic stirrer was 0 (no stirring), 150, 300, 450, 600, and 750 rpm, and the experiment was performed three times under each condition.

  Moreover, what showed the highest value among the obtained signal strength values was converted into a full scale value, and it was set as the relative signal strength.

  FIG. 5 shows a graph in which the relative signal intensity is plotted against the rotational speed of the magnetic stirrer. In FIG. 5, ● represents the average value of three experiments using 0.1 mg-Se / L selenite ion aqueous solution, and ○ represents a sample (distilled water) in which tetravalent selenium is not dissolved. It represents the average of the three experiments used. Error bars represent the maximum and minimum values in three experiments.

  From the result when 0.1 mg-Se / L selenite ion aqueous solution is used (● in FIG. 5), when the rotational speed of the magnetic stirrer is in the range of 0 to 450 rpm, the rotational speed increases. As a result, the relative signal intensity tended to increase gradually, but it was found that the relative signal intensity became a constant value when the rotational speed reached 600 rpm or more. Therefore, if the volume of the stirring solution is within the range of 15 mL (volume of the solution in the Erlenmeyer flask before adding the sodium tetrahydroborate solution) to 25 mL (volume of solution in the Erlenmeyer flask after adding the sodium tetrahydroborate solution) For example, the highest relative signal intensity was obtained at around 600 rpm. And from this result, it was suggested that the quantitative analysis of the analytical sample in which 0.1 mg-Se / L tetravalent selenium, which is the selenium drainage standard value, is dissolved is possible.

  On the other hand, the relative signal intensity is zero even when tetravalent selenium is not dissolved, based on the result of using a sample (distilled water) in which tetravalent selenium is not dissolved (circle in FIG. 5). It was confirmed that there was a case not to become. From these results, there was a concern that hydrogen would be an interfering component during measurement of hydrogen selenide using a potentiostatic sensor and affect the measured value of hydrogen selenide.

  Therefore, the conditions under which the amount of hydrogen generated per unit time is suppressed to an amount that does not affect the measured value of hydrogen selenide were investigated.

First, the solution concentration of sodium tetrahydroborate (NaBH ₄ ), which is a reagent for generating hydrogen selenide by reacting with tetravalent selenium (selenite ion) dissolved in the sample for analysis, was examined. .

  To a mixed solution (acid sample) of 5.0 mL of distilled water and 10 mL of aqueous hydrochloric acid (6 mol / L, 1 + 1), 10 mL of each concentration of sodium tetrahydroborate solution (addition rate: 5 mL to 20 mL / min) was added. Immediately after that, the signal intensity value was measured continuously for 15 minutes by a constant potential electrolytic sensor. Under this experimental condition, it is considered that hydrogen is the only gas that can be detected by the potentiostatic sensor, and therefore, knowledge about the amount of hydrogen generated can be obtained from the signal intensity value. The sodium tetrahydroborate solution was prepared by diluting sodium tetrahydroborate with a 0.1 mol / L sodium hydroxide aqueous solution. The concentration of the sodium tetrahydroborate solution was 1, 3, 4, 5, 10 g / L, and experiments were performed three times for each concentration condition. During the experiment, the rotational speed of the magnetic stirrer was set to 450 rpm.

  Of the obtained signal intensity values, the one showing the highest value was converted to a full scale value to obtain the relative signal intensity.

  FIG. 6 shows a graph plotting relative signal intensity against sodium tetrahydroborate solution concentration. In FIG. 6, ● represents the average value of three experiments, and the error bar represents the maximum value and the minimum value of three experiments. When the concentration of the sodium tetrahydroborate solution was 1 and 3 g / L, the relative signal intensity was zero, but at 4 g / L, the relative signal intensity was 0.005, and the concentration of the sodium tetrahydroborate solution was further increased. As the concentration increased, the relative signal intensity increased. From this result, when the addition rate is 5 mL to 20 mL / min and the concentration of the sodium tetrahydroborate solution is 4 g / L or more, there is a possibility that hydrogen in an amount that interferes with the measurement of hydrogen selenide is generated per unit time. It became clear. On the other hand, when the concentration of the sodium tetrahydroborate solution was 1 and 3 g / L, it was revealed that the amount of hydrogen generated per unit time was sufficiently low so as not to interfere with the measurement of hydrogen selenide. Therefore, it was found that the amount of hydrogen generated per unit time can be suppressed to an amount that does not affect the measured value of hydrogen selenide by setting the concentration of the sodium tetrahydroborate solution to 3 g / L or less.

  Next, the correlation between the rate of addition of sodium tetrahydroborate solution and the amount of hydrogen generation was examined.

  To a mixed solution (acidic sample) of 5.0 mL of distilled water and 10 mL of aqueous hydrochloric acid (6 mol / L, 1 + 1), 10 mL of each concentration of sodium tetrahydroborate solution was added at various addition rates, and immediately after that, a constant potential was added. The signal intensity value was measured continuously by an electrolytic sensor for 10 minutes. Even under this experimental condition, it is considered that hydrogen is the only gas that can be detected by the potentiostatic sensor, and therefore, knowledge about the amount of hydrogen generated can be obtained from the signal intensity value. The sodium tetrahydroborate solution was prepared by diluting in the same manner as described above, and its concentration was 1, 3, 5, 10 g / L. The addition rate was determined by measuring the time until the completion of dropping while changing the dropping rate of the separatory funnel so as to be 1.0 to 40 mL / min. One experiment was performed for each condition. During the experiment, the rotational speed of the magnetic stirrer was set to 450 rpm.

  Of the obtained signal intensity values, the one showing the highest value was converted to a full scale value to obtain the relative signal intensity.

FIG. 7 shows a graph in which the relative signal intensity is plotted against the addition rate of the sodium tetrahydroborate solution. When the concentration of the sodium tetrahydroborate solution was 1 g / L, the relative signal intensity was zero in the studied addition rate range. When the concentration of the sodium tetrahydroborate solution was 3 g / L, the relative signal intensity was zero when the addition rate was in the range of 2.9 to 26 mL / min. However, when the concentration was 36 mL / min, the relative signal intensity was 0. The generation of hydrogen was confirmed. When the concentration of the sodium tetrahydroborate solution was 5 and 10 g / L, the relative signal intensity tended to increase as the addition rate increased. Therefore, the addition rate of the sodium tetrahydroborate solution is set to the following conditions (a) to (c) with respect to 15 mL of the sample for acidic analysis, so that the amount of hydrogen generated per unit time is reduced to hydrogen selenide. It was determined that the amount could not be affected by the measured value.
(A) 38 mL / min or less when sodium tetrahydroborate solution is 1 g / L (b) 26 mL / min or less when sodium tetrahydroborate solution is 3 g / L (c) When sodium tetrahydroborate solution is 5 g / L 8mL / min or less

Therefore, the conditions (a) to (c) are further examined. First, when the conditions (a) to (c) are converted into values for the acidic analysis sample 1L, the following results are obtained.
(A ′) 2.5 L / min or less when sodium tetrahydroborate solution is 1 g / L (b ′) 1.7 L / min or less when sodium tetrahydroborate solution is 3 g / L (c ′) sodium tetrahydroborate 0.5L / min or less when the solution is 5g / L

Next, regarding the conditions (a ′) to (c ′), when the addition rate of the sodium tetrahydroborate solution is converted into the addition rate of sodium tetrahydroborate dissolved in the sodium tetrahydroborate solution, it is as follows. Become.
(A ″) (1 g / L) × (2.5 L / min) = 2.5 g / min: 2.5 g / min or less (b ″) (3 g / L) × (1.7 L / min) = 5 g / min: 5 g / min or less (c ″) (5 g / L) × (0.5 L / min) = 2.5 g / min: 2.5 g / min or less

  That is, by setting the conditions (a ″) to (c ″), the amount of hydrogen generated per unit time can be suppressed to an amount that does not affect the measured value of hydrogen selenide.

  Here, when the sodium tetrahydroborate solution is 5 g / L, the signal intensity does not become zero when the concentration is 13 mL / min or more with respect to 15 mL of the acidic analysis sample. When the same calculation as described above is performed for the addition rate of 13 mL / min when the sodium tetrahydroborate solution is 5 g / L, the rate is 4.3 g / min. In addition, when the sodium tetrahydroborate solution was 10 g / L, the signal intensity did not become zero even when the addition rate was 1 mL / min with respect to 15 mL of the sample for acidic analysis. It is not preferable to set the concentration of the solution to 10 g / L. On the other hand, from the viewpoint of rapidly reducing tetravalent selenium to hydrogen selenide, it is preferable to increase the addition rate of sodium tetrahydroborate.

  Considering the above, when the concentration of the sodium tetrahydroborate solution is more than 3 g / L and not more than 5 g / L, the addition rate of sodium tetrahydroborate is most preferably 4 g / min with respect to 1 L of the acidic analysis sample. It is considered preferable. When the concentration of the sodium tetrahydroborate solution is 3 g / L or less, it is considered to be most preferable to set the concentration to 5 g / min with respect to 1 L of the acidic analysis sample.

  Next, an experiment was conducted to confirm how much of tetravalent selenium dissolved in the analytical sample was reduced to hydrogen selenide.

  A mixed solution (acidic analysis) of 5.0 mL of a standard solution (solvent: distilled water) having a selenite ion concentration of 0.5 mg-Se / L or 1.0 mg-Se / L and an aqueous hydrochloric acid solution (6 mol / L, 1 + 1) 10 g (addition rate: 10 to 15 mL / min) of 3 g / L sodium tetrahydroborate solution was added to the sample for use to reduce tetravalent selenium to hydrogen selenide. And the sample for acidic analysis before and after the sodium tetrahydroborate solution addition was measured by the hydride generation ICP emission analysis method (HG-ICP-AES) prescribed | regulated by JIS-K0102.67.3. The experiment was performed three times for each condition, and the rotational speed of the magnetic stirrer was 600 rpm during the experiment. The results are shown in Table 1.

  From the results shown in Table 1, it was revealed that the unreacted amount of tetravalent selenium was less than 10%. That is, it became clear that 90% or more of the tetravalent selenium dissolved in the sample was reduced to hydrogen selenide.

  Next, the correlation between pH and signal intensity of the sample for acid analysis was examined.

  In 5 mL of 0.1 mg-Se / L selenite ion aqueous solution, 0.06, 0.2, 0.6, 2, 3 or 6 mol / L (0.06, 0.2, 0.6, 2, 3 Alternatively, 10 mL of 3 g / L sodium tetrahydroborate solution (addition rate: 10 mL to 15 mL / min) is added to each sample for acidic analysis to which 10 mL of an aqueous hydrochloric acid solution of 6 N / L) is added. The signal intensity value was measured continuously for 10 minutes by the sensor. The experiment was performed three times for each condition, and the rotational speed of the magnetic stirrer was 600 rpm during the experiment.

  Moreover, what showed the highest value among the obtained signal strength values was converted into a full scale value, and it was set as the relative signal strength.

  The results are shown in Table 2 and FIG. It was found that an appropriate relative signal intensity can be obtained when the concentration of the hydrochloric acid aqueous solution added as an acid to the analysis sample is 3 mol / L and 6 mol / L. However, it was found that when the concentration of the hydrochloric acid aqueous solution added as an acid to the analytical sample is 0.2 mol / L or more, a signal intensity of about 60% can be obtained as compared with an appropriate relative signal intensity. Therefore, the concentration of the aqueous hydrochloric acid solution added as an acid to the analytical sample may be 0.2 mol / L or more, but is preferably 0.6 mol / L or more, more preferably 2 mol / L or more. It turned out that it is more preferable to set it as 3 mol / L or more.

  Here, when the pH after completion of measurement was measured under each condition, the pH was 0.4 or less when the concentration of the hydrochloric acid aqueous solution added as an acid to the analysis sample was 3 mol / L or more. Was confirmed. From this result, it became clear that an appropriate relative signal intensity can be easily obtained by adjusting the pH of the sample for acidic analysis so that the pH after addition of the sodium tetrahydroborate solution is 0.4 or less.

  Here, when the concentration of the aqueous hydrochloric acid solution added as an acid to the analytical sample is 2 mol / L or more, the pH of the aqueous solution itself and the pH of the acidic analytical sample adjusted using the aqueous solution may show negative values. Indicated. Therefore, the pH of the acidic analysis sample before addition of the sodium tetrahydroborate solution could not be accurately defined. However, when 10 mL of hydrochloric acid aqueous solution having a concentration of 3 mol / L or more is added to 5 mL of analysis sample, it was confirmed that the pH was 0.4 or less. It is considered that it should be at least 2 mol / L or more. Therefore, it was shown that the pH after completion of the measurement was 0.4 or less by adjusting the pH of the acidic analysis sample to the same level as the pH of an aqueous hydrochloric acid solution of 2 mol / L or more.

  Based on the above experimental results, the quantitative evaluation was examined.

  Selenite ion concentration is 0.01, 0.05, 0.1, 0.5 or 1.0 mg-Se / L standard solution (solvent: distilled water) 5.0 mL and hydrochloric acid aqueous solution (6 mol / L, 1 + 1) 10 mL of a 3 g / L sodium tetrahydroborate solution (addition rate: 10 to 15 mL / min) is added to 10 mL of the mixed solution (sample for acidic analysis), and is continued for 10 minutes by a potentiostatic sensor. Signal strength values were measured. The sodium tetrahydroborate solution was prepared by diluting sodium tetrahydroborate with a 0.1 mol / L sodium hydroxide aqueous solution. Moreover, it experimented once about each density | concentration conditions, and the rotation speed of the magnetic stirrer was 600 rpm during experiment.

  FIG. 8 shows signal profiles plotting relative signal intensities with respect to time in standard solutions of various selenite ion concentrations. From this result, the time required from the start of adding the sodium tetrahydroborate solution to the end of the measurement is within 6 minutes when performing quantitative analysis with area intensity, and within 4 minutes when performing quantitative analysis with peak intensity. In each case, it became clear that the measurement was completed within 10 minutes from the start of adding the sodium tetrahydroborate solution. Moreover, the signal intensity value in the case of using a standard solution having a selenite ion concentration of 1.0 mg-Se / L was out of the measurement range of the constant potential electrolytic sensor. Considering the signal profile in the standard solution of selenite ion concentration shown in FIG. 8, the maximum detected concentration of selenium in water of the potentiostatic sensor was determined to be about 0.7 mg-Se / L.

  Next, calibration curves were prepared using standard solutions of various selenite ion concentrations.

  Selenite ion concentration is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.5, To a mixed solution (sample for acidic analysis) of a 0.7 mg-Se / L standard solution (solvent: distilled water) and hydrochloric acid aqueous solution (6 mol / L, 1 + 1) (3 g / L sodium tetrahydroborate solution) (Addition rate: 10 to 15 mL / min) was added, and the signal intensity value was measured continuously for 10 minutes by a constant potential electrolytic sensor. The sodium tetrahydroborate solution was prepared by diluting sodium tetrahydroborate with a 0.1 mol / L sodium hydroxide aqueous solution. Moreover, it experimented 3 times about each density | concentration conditions, and the rotation speed of the magnetic stirrer was 600 rpm during experiment.

  A calibration curve created from the peak values of the obtained signal profile is shown in FIG. In the range of 0.01 to 0.7 mg-Se / L, an extremely high calibration curve (correlation coefficient 0.999) was obtained. The correlation coefficient was 0.988 even in the low concentration range of 0.01 to 0.1 mg-Se / L, and it was confirmed that extremely high linearity was obtained in the low concentration range. The lower limit of detection (σ = 3) was 0.0035 mg-Se / L, and the lower limit of quantification (σ = 10) was 0.012 mg-Se / L. The coefficient of variation (RSD) was 14.0% at 0.01 mg-Se / L and 3.85% at 0.1 mg-Se / L. The reason why the coefficient of variation is high at 0.01 mg-Se / L is that the signal intensity value of hydrogen selenide was recorded by integer recording at intervals of 1.25 ppb, resulting in low resolution. It is estimated that the coefficient of variation can be suppressed by measuring the value by analog output.

  Next, FIG. 10 shows a calibration curve created by calculating the area intensity of the obtained signal profile. In the range of 0.01 to 0.7 mg-Se / L, an extremely high calibration curve (correlation coefficient 0.994) was obtained. The correlation coefficient was 0.964 even in the low concentration range of 0.01 to 0.1 mg-Se / L, and it was confirmed that extremely high linearity was obtained even in the low concentration range. The lower limit of detection (σ = 3) was 0.0026 mg-Se / L, and the lower limit of quantification (σ = 10) was 0.0087 mg-Se / L. The coefficient of variation (RSD) was 12.9% at 0.01 mg-Se / L and 5.5% at 0.1 mg-Se / L. The reason why the correlation coefficient in the case of FIG. 10 is lower than that in the case of FIG. 9 is considered to be caused by the measurement interval of the signal intensity value being 10 seconds. It is estimated that the correlation coefficient increases by shortening.

  In any case, since extremely high linearity was obtained in the tetravalent selenium concentration range of 0.01 to 0.7 mg-Se / L, the tetravalent selenium concentration of the sample for analysis was within this concentration range. It became clear that quantitative analysis can be performed with extremely high accuracy. Therefore, according to the quantitative analysis method of the present invention, not only the current selenium drainage standard value of 0.1 mg-Se / L but also the drainage standard value is further reduced, Quantitative analysis of tetravalent selenium concentration is possible.

(Example 2)
Experiments were performed using the experimental apparatus shown in FIG. In addition, this experiment was also conducted under normal temperature and normal pressure in view of meeting the needs for on-site analysis. Therefore, the conditions obtained from this experimental result can be applied under normal temperature and pressure.

A mixed solution (a sample for acidic analysis) 2 a of 5.0 mL of a sample containing tetravalent selenium and 10 mL of a predetermined concentration hydrochloric acid (HCl) aqueous solution was introduced into the reaction vessel (container) 2. 10 mL of an aqueous solution of sodium tetrahydroborate (NaBH ₄ ), which is a reducing agent, was sent to the reaction vessel 2 and mixed with the stirrer 33 to generate hydrogen selenide (H ₂ Se) gas. The flow rate of sodium tetrahydroborate solution 3a having a predetermined concentration was controlled by a peristaltic pump (addition means) 3. Hydrogen selenide produced in the reaction vessel 2 was introduced into the potentiostatic sensor 4 with pure air as a carrier gas. The carrier gas was supplied by the carrier gas supply means 7. The carrier gas supply means 7 comprises a pure air cylinder 7a, a pressure regulator 7b, a pressure gauge 7c, a mass flow controller 7d, and a stop valve 7e, and the flow rate was controlled by the mass flow controller 7d. As the constant potential electrolytic sensor 4, a hydrogen selenide gas detector (PS-7 manufactured by New Cosmos Electric Co., Ltd.) was used, and CDS-7, which is a dedicated sensor unit for hydrogen selenide (H ₂ Se), was also used. This constant potential electrolytic sensor has a gas suction amount of 500 mL / min, a hydrogen selenide measurement range of 1 to 275 ppb, and an indication accuracy within 10% of the full scale. The measurement data was recorded in the personal computer 34 via the A / D converter 32. The A / D converter 32 has a minimum data acquisition cycle of 10 Hz and a minimum resolution of 0.4% with respect to full scale. For analysis of the measurement data, Smart Chrom (manufactured by Kwai Technologies) was used. Since the hydrogen selenide gas is very toxic, the hydrogen selenide gas after the measurement was passed through the abatement tank 6 for detoxification. For removing hydrogen selenide, an aqueous copper sulfate solution 6a was used. The gas after passing through the detoxification tank was measured by the detoxification confirmation detector 31 to confirm the presence or absence of hydrogen selenide. As the decontamination confirmation detector 31, a hydrogen selenide gas detector (PS-7 manufactured by New Cosmos Electric Co., Ltd.) was used.

  In this example, the signal acquisition of hydrogen selenide was carried out by an analog method instead of the digital method as in Example 1. The data acquisition interval was 0.1 second, and the minimum resolution with respect to full scale was 0.4%. That is, the signal intensity interval (plot interval) is 0.4 ppb, and the fractional part is rounded down. Similar to Example 1, the selenium concentration was calculated based on the peak intensity of the signal profile or the area value of the signal profile. The area value was calculated using spreadsheet software Origin (registered trademark).

  In this example, a selenium standard solution (aqueous solution having a tetravalent selenium concentration of 1000 mg / L) diluted with distilled water to a predetermined concentration was used as a test sample. Moreover, the sodium tetrahydroborate solution used what melt | dissolved predetermined amount sodium tetrahydroborate in 0.1 mol / L sodium hydroxide aqueous solution was used. Moreover, ethylenediaminetetraacetic acid (EDTA) was dissolved in this sodium hydroxide aqueous solution so that it might become 1.0 mmol / L.

(1) Examination of analysis conditions (1-1) Examination of carrier gas flow rate A calibration curve (selenium concentration 0.01 to 0.5 mg / L, n = 3) was prepared by changing the carrier gas flow rate, and the lower limit of quantification ( σ = 10) and the upper limit of quantification were examined.

  The conditions other than the carrier gas flow rate were as follows: the sodium tetrahydroborate solution concentration was 3.0 g / L, the sodium tetrahydroborate solution flow rate was 20 mL / min, and the hydrochloric acid concentration in the hydrochloric acid aqueous solution was 6.0 mol / L. . The upper limit of quantification was calculated from the calibration curve of the selenium concentration in water relative to the upper limit of detection of the potentiostatic sensor 4 (275 ppb as hydrogen selenide). Further, 5 mL of the test sample and 10 mL of hydrochloric acid aqueous solution were mixed to obtain a sample for acidic analysis. The calibration curve was created from signal intensity data (peak value, area value) with respect to the selenium concentration in water, as in Example 1.

  The experimental results are shown in FIG. The lower limit of quantification was not as great as 0.02 to 0.04 mg / L in all the carrier gas flow rates verified. However, with regard to the upper limit of quantification, a large difference was observed depending on the carrier gas flow rate, and it was confirmed that the quantitative improvement was significantly improved by increasing the carrier gas flow rate from 400 mL / min to 500 mL / min. Moreover, although the same experiment was done also in the range of carrier gas flow rates 800-1000 mL / min, it was not able to measure. This was presumed to be because a large amount of carrier gas gave a burden to 500 mL / min, which is the gas suction amount of the potentiostatic sensor 4.

  From the above results, the carrier gas flow rate is preferably 500 to 700 mL / min, more preferably 500 mL / min, which has a wide selenium measurement range and less burden on the potentiostatic sensor 4. I understood.

(1-2) Examination of concentration of sodium tetrahydroborate solution The effect of change in sodium tetrahydroborate concentration on signal intensity was examined.

  As a test sample, a 0.25 mg / L selenium standard solution and distilled water (blank sample) were used. The experiment was conducted under conditions other than the sodium tetrahydroborate concentration at a carrier gas flow rate of 500 mL / min, a sodium tetrahydroborate solution addition flow rate of 20 mL / min, and a hydrochloric acid concentration of the hydrochloric acid aqueous solution of 6.0 mol / L. Further, 5 mL of the test sample and 10 mL of hydrochloric acid aqueous solution were mixed to obtain a sample for acidic analysis.

The results are shown in FIG. As the sodium tetrahydroborate concentration increased, the signal intensity in the selenium standard solution tended to increase. Sodium tetrahydroborate concentration 4 g / L Above this, an increase in signal intensity was observed in the blank sample. This is considered to be because a large amount of hydrogen gas was generated by increasing the sodium tetrahydroborate concentration, which hindered the measurement of hydrogen selenide. In gas measurement in a constant potential electrolytic sensor, it has been reported that hydrogen adsorbed on the surface of the sensor film is electrolyzed and hydrogen ions increase, causing interference during measurement.
・ T. Ishiji, T. Iijima, and K. Takahashi: “Electrochemical sensing of arsine and silane by the amperometric gas sensor by using gold electrode”, Denki Kagaku, 64 (12), 1304-1310 (1996).
-Toru Ishiji: "Development of a new electrochemical sensor for environmental gas monitoring", Electrochem., 69 (4), 285-288 (2001).
・ Y. Mizutani, H. Matsuda, T. Ishiji, N. Furuya, and K. Takahashi: “Improvement of electrochemical NO ₂ sensor by use of carbon-fluorocarbon gas permeable electrode”, Sens. Actuators B, 108, 815-819 (2005).

  From the above results, in order to prevent hydrogen gas from interfering in the measurement of hydrogen selenide, when the addition flow rate of sodium tetrahydroborate solution is 20 mL / min, the concentration of sodium tetrahydroborate is 3 g / It was found that it is preferably L or less, and more preferably 3 g / L at which the highest signal intensity can be obtained.

(1-3) Examination of Addition Flow Rate of Sodium Tetrahydroborate Solution The effect of change in addition flow rate of sodium tetrahydroborate solution on the signal intensity was examined.

  As a test sample, a 0.25 mg / L selenium standard solution was used. The experiment was conducted under conditions other than the addition flow rate of the sodium tetrahydroborate solution at a carrier gas flow rate of 500 mL / min, a sodium tetrahydroborate solution concentration of 3.0 g / L, and a hydrochloric acid concentration of 6.0 mol / L. Further, 5 mL of the test sample and 10 mL of hydrochloric acid aqueous solution were mixed to obtain a sample for acidic analysis.

  First, FIG. 15A shows the result of examining the influence of the addition flow rate of the sodium tetrahydroborate solution on the peak height value of the signal profile. The signal intensity tended to increase until the addition flow rate was 25 mL / min, but was almost constant from 25 to 90 mL / min. This is presumably because hydrogen selenide is generated in a short time and the peak becomes sharp when the flow rate of the sodium tetrahydroborate solution increases. Moreover, it is considered that the signal intensity became constant when the addition flow rate was 25 mL / min or more because the absolute amount of sodium tetrahydroborate added per unit time satisfied the amount necessary for hydrogen selenide production.

  Next, FIG. 15B shows the results of examining the influence of the addition flow rate of the sodium tetrahydroborate solution on the area value of the signal profile. The area value tended to decrease as the addition flow rate increased. When the addition flow rate is small, it takes time to produce hydrogen selenide, and the area value is considered to increase as the peak width increases.

  Therefore, the influence of the addition flow rate of the sodium tetrahydroborate solution on the half width of the signal profile was examined. The result is shown in FIG. 15C. It was found that the full width at half maximum tends to decrease and the peak tends to become sharper as the addition flow rate increases. Moreover, when the addition flow rate was excessive, hydrogen selenide was generated in a short time, and the reproducibility tended to deteriorate.

  From the above results, it was found that when the addition flow rate of the sodium tetrahydroborate solution was 25 to 50 mL / min, the signal intensity was high, the peak was sharp, and the reproducibility was good in the plot at the height value. . Therefore, it was found that the addition flow rate of the sodium tetrahydroborate solution is preferably set to 25 to 50 mL / min, and more preferably set to 30 mL / min.

Here, since the concentration of the sodium tetrahydroborate solution was 3.0 g / L, the addition flow rate of the sodium tetrahydroborate solution was set to be the same as that in Example 1 with respect to 1 L of the sample for acidic analysis. When converted to the addition rate, the following results are obtained.
25-50 mL / min → 5-10 g / min 30 mL / min → 6 g / min

(1-4) Influence of hydrochloric acid concentration The influence of the change in the hydrochloric acid concentration of the aqueous hydrochloric acid solution for acidifying the test sample on the signal intensity was examined.

  As a test sample, a 0.25 mg / L selenium standard solution was used. The experiment was conducted under conditions other than the hydrochloric acid concentration at a carrier gas flow rate of 500 mL / min, a sodium tetrahydroborate solution concentration of 3.0 g / L, and a sodium tetrahydroborate solution addition flow rate of 30 mL / min. Further, 5 mL of the test sample and 10 mL of hydrochloric acid aqueous solution were mixed to obtain a sample for acidic analysis.

  The experimental results are shown in FIG. The signal intensity was highest at a hydrochloric acid concentration of 6.0 to 10.0 mol / L, but it was found that a signal intensity sufficient for quantitative analysis of selenium was obtained in the entire experimental range. However, when selenium remaining in the aqueous solution in the reaction vessel 2 was measured after the reaction was completed, 0.03 mg / L selenium was detected when the hydrochloric acid concentration was 12.0 mol / L. From this, it was judged that setting the hydrochloric acid concentration to more than 10.0 mol / L is not preferable because unreacted selenium may remain in the reaction tank 2 and the amount of hydrochloric acid used increases.

  Even when the hydrochloric acid concentration was 1.0 or 3.0 mol / L, selenium remained in the aqueous solution in the reaction tank 2 after the completion of the reaction, but the amount was as small as 0.01 mg / L. It was a thing.

  In Example 1, when the hydrochloric acid concentration was 0.2 mol / L, a signal intensity of about 60% of the appropriate relative signal intensity was obtained, so that the hydrochloric acid concentration was 0.2 mol / L or more. Provides a signal intensity sufficient for quantitative analysis of selenium.

  Therefore, the hydrochloric acid concentration may be 0.2 to 10 mol / L, preferably 1.0 to 10 mol / L, more preferably 2.0 to 10 mol / L, and 3.0 to It was found that the concentration was more preferably 10 mol / L, and still more preferably 6.0 to 10 mol / L. Here, considering the signal intensity value obtained with respect to the amount of hydrochloric acid used, it was considered that 6.0 mol / L was most preferable.

  In this example, 10 mL of hydrochloric acid aqueous solution was mixed with 5 mL of the test sample. Therefore, when expressed by the default value of acid by hydrochloric acid of the sample for acidic analysis, the default value of acid by hydrochloric acid of the sample for acidic analysis is 0.13-6.7 N / L, preferably 0.67-6.7 N / L, more preferably 1.3-6.7 N / L, 2.0 -6.7 N / L is more preferable, 4.0 -6.7 N / L is still more preferable, and 4.0 N / L is most preferable. In particular, by setting to 4.0 to 6.7 N / L, a sufficient signal intensity value can be obtained, and selenium dissolved in the analysis sample can be efficiently hydrogenated.

(1-5) Quantitative evaluation The conditions obtained in the above (1) to (4), that is, carrier gas flow rate 500 mL / min, sodium tetrahydroborate solution concentration 3.0 g / L, sodium tetrahydroborate solution Quantitative evaluation was performed when the addition flow rate was 30 mL / min and the hydrochloric acid concentration was 6.0 mol / L. Further, 5 mL of the test sample and 10 mL of hydrochloric acid aqueous solution were mixed to obtain a sample for acidic analysis.

  A calibration curve was prepared in the range of selenium concentration of 0.01 to 0.5 mg / L under the above analysis conditions. The results are shown in FIGS. 18A and 18B. In addition, FIG. 19 shows the measurement profile used to create the calibration curve.

  In the calibration curve (FIG. 18A) obtained by plotting the peak height of the signal profile against the selenium concentration, the lower limit of detection (σ = 3) is 0.002 mg / L, and the lower limit of quantification (σ = 10) is 0.00. It was 005 mg / L.

  In the calibration curve (FIG. 18B) obtained by plotting the area value of the signal profile against the selenium concentration, the detection lower limit (σ = 3) is 0.01 mg / L, and the lower limit of quantification (σ = 10) is 0.04 mg. / L.

  As a result of comparing the calibration curve based on the height value and the area value, the lower limit of quantification was such that the height value was 1/10 or less of the area value. Table 3 shows the results of reproducibility obtained at each selenium concentration. Reproducibility was evaluated by Relative Standard Deviation (RSD). The reproducibility of the selenium concentration of 0.01 mg / L was 19.9% in terms of area value and 4.6% in terms of height value.

  From the above results, it was determined that the plotting with the height value was higher than the area value, and the quantitativeness was higher, and the evaluation with the height value was more appropriate. Moreover, the time required from the start of addition of the sodium tetrahydroborate solution to the end of the measurement was within 3 minutes, and tetravalent selenium could be measured quickly and with high sensitivity.

  Further, regarding the calibration curve obtained by plotting with the peak height of the signal profile against the selenium concentration, the correlation coefficient of the calibration curve is comparable when compared with the calibration curve obtained in Example 1 (FIG. 9). However, the signal output stability (reproducibility) at a selenium concentration of 0.01 mg / L was improved from 14.0% to 4.6% (Table 3).

  The improvement in reproducibility was the use of carrier gas, the setting of analysis parameters, and the resolution of the constant potential electrolytic sensor 4 was higher than that of the constant potential electrolytic sensor 4 used in Example 1, as shown in FIG. It is thought to be caused by

(2) Examination of application to desulfurization effluent discharged from coal-fired power plant (2-1) Desulfurization effluent sample Three types of desulfurization effluent from coal-fired power plant were obtained in order to evaluate the applicability to actual effluent. An ICP emission analyzer (ICP-AES, SPS-5000 manufactured by Seiko Instruments Inc.) and ion chromatography (IC, DX-320 manufactured by Dionex) were used for measuring the wastewater composition.

  In the official method (JIS K0102 67.3), the measurement of selenium by chemical form is not clearly defined. Therefore, the measurement of selenium according to its form was carried out by the method of Kanda et al. (Hiroshi Kanda, Hiroyuki Akibo, Yuzo Shirai, Shigeo Ito: “Chemical form of selenium in coal-fired power plant desulfurization equipment”, Central Research Institute of Electric Power Research Institute, M04015, (2005) .). An outline of this analysis method is shown in FIG. First, 50 mL of a drainage sample was filtered to remove impurities, and then sulfuric acid and nitric acid were added and heated (170 ° C.) until sulfuric acid white smoke was generated to decompose organic substances (acid decomposition). Next, the acid-decomposed sample was allowed to cool, adjusted to 50 mL with distilled water, and then the tetravalent selenium concentration was measured by hydrogen compound generation ICP-AES (HG-ICP-AES). Moreover, after acid-decomposing the sample, hydrochloric acid was added and heated at 120 ° C. for 10 minutes to reduce hexavalent selenium (reduction treatment), and the total selenium concentration was measured by HG-ICP-AES. The hexavalent selenium concentration was determined from the difference between the total selenium concentration and the tetravalent selenium concentration.

  Table 4 shows the chemical composition of the desulfurization effluent used. Desulfurization effluent A had a higher salt concentration than the other two, and contained 0.275 mg / L tetravalent selenium and 0.267 mg / L hexavalent selenium. The desulfurization waste water B contained tetravalent selenium 0.057 mg / L and hexavalent selenium 0.049 mg / L, and the desulfurization waste water C contained tetravalent selenium 0.003 mg / L and hexavalent selenium 0.027 mg / L.

(2-2) Measurement of desulfurization effluent Desulfurization effluents A, B and C were mixed with a carrier gas flow rate of 500 mL / min, a sodium tetrahydroborate solution concentration of 3.0 g / L, and a tetrahydroborate sodium solution addition flow rate of 30 mL / min. When measurement was performed with a hydrochloric acid concentration of 6 mol / L, the signal value showed a negative value in any desulfurization effluent, and an accurate signal value could not be obtained.

  Accordingly, for desulfurization wastewater B, first, only the desulfurization wastewater B was introduced into the reaction tank 2, and the signal value was measured by flowing a carrier gas at 500 mL / min while adding hydrochloric acid. It showed a negative value, and then the signal value gradually increased and recovered to near zero. Therefore, after the signal value was recovered, a sodium tetrahydroborate solution having a concentration of 3.0 g / L was added at an addition flow rate of 30 mL / min, and the carrier gas was supplied at 500 mL / min, and the signal value was measured. No signal value was obtained (FIG. 21). This result was the same for the desulfurization effluents A and C.

  From this, it was found that the coexisting substances in the desulfurization effluent were vaporized by the addition of hydrochloric acid, hindering the signal output of the hydrogen selenide gas detector. In addition, since the signal value of hydrogen selenide was not obtained after the signal was recovered, the interference in the measurement of hydrogen selenide was the inhibition of hydrogen selenide gas production and the signal of the potentiostatic sensor 4 (PS-7). It was found that the output was largely divided into output disturbance.

(2-3) Examination of factors that inhibit the formation of hydrogen selenide In order to confirm substances that inhibit the hydrogenation reaction of selenium, the wastewater components (24 components in Table 4) having a predetermined concentration were added to 0.1 mg / L of selenium. The tetravalent selenium concentration was measured by HG-ICP-AES after adding to the standard solution.

As a result, it was confirmed that hydrogen selenide production was not inhibited except for copper (2). Copper (2) inhibited the hydrogenation of tetravalent selenium when it was present at a concentration (weight ratio) 10 times or more that of tetravalent selenium. This is to produce copper selenide from hydrogen selenide and copper (2) by the following reaction (M. Thompson, B Pahlavanpour, SJ Walton: “Simultaneous determination of trace concentration of arsenic, antimony, bismuth, selenium and tellurium in aqueous solution by introduction of the gaseous hydride into an inductively plasma source for emission spectrometry ”, Analyst, 103, 568-579 (1978)).
4SeO ₃ ²⁻ + 3BH ₄ ⁻ + 11H ⁺ → 4H ₂ Se + 3H ₃ BO ₃ + 3H ₂ O
H ₂ Se + Cu ²⁺ → CuSe ↓ + H ₂

  However, as shown in Table 4, since the concentration of copper (2) is low in the desulfurization effluent (Table 1), there is little possibility that this will inhibit the hydrogenation of selenium. According to D'Ulivo et al., Copper (2) is 10 times, iron (3) is 5000 times, nickel (2) is 200 times, cobalt (2) is 5000 times, and gold (3) is 5 times that of selenium. There is a report that hydrogenation is inhibited when coexistence of platinum (4) is 150 times, silver (1) is 30 times, and palladium (2) is 20 times (A. D'Ulivo, L. Ganfranceschi, L. Lampugnani, R. Zamboni: “Masking agents in the determination of selenium by hydride generation technique”, Spectro. Acta B, 57, 2081-2094 (2002).) It was found that the hydrogenation of selenium was not hindered because it was low. From the above, it was found that the main coexisting components in the desulfurization effluent do not inhibit the production of hydrogen selenide.

(2-4) Interference of hydrogen selenide gas detector signal output The drainage components that interfere with the signal output of the constant potential electrolysis sensor 4 were examined. In the same manner as described above, drainage components having a predetermined concentration (24 types of all components in Table 4) were added to a 0.1 mg / L selenium standard solution, and measurement was performed with a potentiostatic sensor 4.

  As a result, only iodide ions interfered with the signal output of the potentiostatic sensor 4. Iodide ions were 0.1 mg / L or more, which interfered with the signal output of the hydrogen selenide gas detector when hydrochloric acid was added.

  FIG. 22 shows the results of measurement while adding hydrochloric acid to a sample prepared by mixing iodide ions in a range of 0.1 to 10 mg-I / L with respect to a 0.1 mg / L selenium standard solution. When hydrochloric acid was added to the sample, the signal intensity showed a negative value. In addition, when the iodide ion concentration was increased, the time for showing a negative signal value became longer.

  Further, after adding hydrochloric acid to the desulfurization effluent and stirring for 20 minutes, the iodide ion concentration in the sample was measured. The concentration of iodide ions in the desulfurization effluents B and C was 5.6 mg-I / L to 1.5 mg-I / L. L decreased from 4.3 mg-I / L to 1.4 mg-I / L. This suggests that the substance produced by the reaction of iodide ions in the desulfurization effluent with hydrochloric acid vaporizes and gives a negative signal value to the hydrogen selenide gas detector.

(2-5) Examination of removal of interfering substances In the JIS method, acid decomposition of organic substances with sulfuric acid and nitric acid is defined as a pretreatment method for selenium in HG-ICP-AES analysis of selenium (JIS-K0102.67. 3.). The desulfurization drainage components after acid decomposition were measured by ICP-AES, and the chemical components in which the concentration change was recognized are shown in Table 5.

  After acid decomposition, iodine, bromine, and chlorine concentrations decreased. The iodide ions in the desulfurization waste water B and the desulfurization waste water C were decreased from 5.6 mg-I / L to 0.5 mg-I / L, and from 4.3 mg-I / L to 0.4 mg-I / L, respectively. Further, the COD values of the desulfurization waste water B and the desulfurization waste water C were reduced from 9.0 mg-O / L to 2.4 mg-O / L and from 26.4 mg-O / L to 18.0 mg-O / L, respectively.

  The result of having measured the selenium in the desulfurization waste water after performing an acid decomposition with the hydrogen selenide gas detector is shown in FIG. Since the tetravalent selenium concentration of the desulfurization waste water C was below the limit of quantification of this apparatus, a sample to which 0.1 mg / L selenium was added before the acid decomposition treatment was used. The measurement conditions were a carrier gas flow rate of 500 mL / min, a sodium tetrahydroborate solution concentration of 3.0 g / L, a sodium tetrahydroborate solution addition flow rate of 30 mL / min, and a hydrochloric acid concentration of 6.0 mol / L. As a result, a good correlation was obtained between the HG-ICP-AES measurement results and the hydrogen selenide gas detector measurement results for the desulfurization effluents A to C. From the above, it was found that acid decomposition treatment is an effective pretreatment method in measurement using a hydrogen selenide gas detector.

  Here, in the above experiment, hydrochloric acid was added after the pretreatment by the JIS method, but without adding hydrochloric acid, and after the pretreatment by the JIS method, without adding hydrochloric acid, the sodium tetrahydroborate solution As a result of the same experiment with addition of hydrogen, it was found that the quantitative analysis of hydrogen selenide is possible, although the signal intensity is reduced to about 70% compared to the case of adding hydrochloric acid.

  Furthermore, instead of adding 6 mol / L (6 N / L) hydrochloric acid to the sample for analysis, 3 mol / L (6 N / L) sulfuric acid or 6 mol / L (6 N / L) nitric acid is added for acid analysis. When a sample was prepared and an experiment was conducted, it became clear that the quantitative analysis of hydrogen selenide was possible for sulfuric acid, although the signal intensity decreased to about 60% compared to the case of using hydrochloric acid. It was. However, no signal intensity was obtained for nitric acid.

  From these results, the reason why the signal intensity that was possible for the quantitative analysis of hydrogen selenide was obtained without adding hydrochloric acid after the pretreatment by JIS method was due to the sulfuric acid used in the pretreatment. It became clear that it was a thing. That is, it became clear that not only hydrochloric acid but also sulfuric acid can be used as an acid for preparing a sample for acid analysis.

  In addition, because the signal intensity of the hydrogen selenide quantitative analysis was obtained only by the pretreatment by the JIS method, the sample for analysis was simultaneously performed by the pretreatment by the JIS method with the removal of organic compounds and iodide ions. It was also revealed that can be acidified.

  However, in order to increase the accuracy of quantitative analysis of selenium, it was found that it is preferable to increase the acidity by adding hydrochloric acid after pretreatment by the JIS method.

It is a figure which shows an example of the quantitative analysis system of selenium concerning 1st embodiment. It is a figure which shows the measurement principle of hydrogen selenide by a constant potential electrolytic sensor. It is a figure which shows an example of the whole structure of an analysis means. It is a figure which shows the experimental apparatus for enforcing the quantitative analysis method of selenium concerning 1st embodiment. In Example 1, it is the graph which plotted the relative signal strength with respect to the rotation speed of the magnetic stirrer. In Example 1, it is the graph which plotted the relative signal strength with respect to the density | concentration of the sodium tetrahydroborate solution. In Example 1, it is the graph which plotted the relative signal strength with respect to the addition rate of the sodium tetrahydroborate solution. In Example 1, it is a figure which shows the signal profile which plotted the relative signal strength with respect to time in the standard solution of various selenite ion concentration. In Example 1, it is a figure which shows the analytical curve produced with the peak value of the signal profile. In Example 1, it is a figure which shows the analytical curve created by calculating the area intensity of a signal profile. In Example 1, it is the graph which plotted the relative signal strength with respect to pH of the sample for acidic analysis after sodium tetrahydroborate addition. It is a figure which shows the experimental apparatus for enforcing the quantitative analysis method of selenium concerning 2nd embodiment. In Example 2, it is a figure which shows the change of the fixed lower limit and fixed upper limit by carrier gas flow volume. In Example 2, it is a figure which shows the influence which the density | concentration of a sodium tetrahydroborate solution has on signal strength. In Example 2, it is a figure which shows the result of having examined about the influence which the addition flow rate of the sodium tetrahydroborate solution has on the peak height value of a signal profile. In Example 2, it is a figure which shows the result of having examined about the influence which the addition flow rate of the sodium tetrahydroborate solution has on the area value of a signal profile. In Example 2, it is a figure which shows the result of having examined about the influence which the addition flow rate of the sodium tetrahydroborate solution has on the half value width of a signal profile. In Example 2, it is a figure which shows the result of having examined about the influence which hydrochloric acid concentration has on signal intensity. It is a figure which shows the outline of the quantitative analysis method according to the form of selenium. In Example 2, it is a figure which shows the analytical curve produced with the peak value of the signal profile. It is a figure which shows the analytical curve produced by calculating the area intensity of a signal profile in Example 2. FIG. In Example 2, it is a figure which shows the signal profile used for the calibration curve preparation. It is the figure which compared the signal profile obtained in Example 1, and the signal profile obtained in Example 2. FIG. It is a figure which shows a time-dependent change of the signal strength when hydrochloric acid and sodium tetrahydroborate are added to desulfurization waste_water | drain. In Example 2, it is a figure which shows the result of having measured the signal intensity | strength, adding hydrochloric acid to the sample which mixed the iodide ion with respect to the selenium standard solution. It is a figure which shows the result of having measured the selenium in the desulfurization waste water after performing an acid decomposition with the hydrogen selenide gas detector. It is a figure which shows an example of the quantitative analysis system of selenium concerning 2nd embodiment.

Explanation of symbols

1, 1 'selenium quantitative analysis system 2 container (reaction tank)
2a Sample for acid analysis 3 Addition means 3a Sodium tetrahydroborate 4 Constant potential electrolytic sensor 5 Analysis means 6 Collection means 6a Copper sulfate solution 7 Carrier gas supply means

Claims (8)

  Adding at least one of hydrochloric acid and sulfuric acid to an analytical sample in which tetravalent selenium is dissolved to obtain an acidic analytical sample having an acid normality of 0.13 to 6.7 N / L; A step of adding sodium tetrahydroborate at a rate of 5 g / min or less to 1 L of an analytical sample, reacting the tetravalent selenium with the sodium tetrahydroborate to generate hydrogen selenide, A step of sucking at 20 mL / min, a step of measuring the sucked hydrogen selenide with a potentiostatic sensor and obtaining a measured value, and a calibration of the tetravalent selenium concentration of the analytical sample based on the measured value A calibration curve used in the calibration curve method is obtained by calculating a tetravalent selenium concentration obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations and a measured value of the potentiostatic sensor. Quantitative analysis method of selenium, characterized in that it was created on the basis of the function.   Adding at least one of hydrochloric acid and sulfuric acid to an analytical sample in which tetravalent selenium is dissolved to obtain an acidic analytical sample having an acid normality of 0.13 to 6.7 N / L; A step of adding sodium tetrahydroborate at a rate of 5 to 10 g / min with respect to 1 L of analytical sample, reacting the tetravalent selenium with the sodium tetrahydroborate to generate hydrogen selenide, and carrier to the hydrogen selenide A step of adding a gas at 500 to 700 mL / min, a step of sucking the hydrogen selenide together with the carrier gas at a rate of 400 to 600 mL / min, and measuring the sucked hydrogen selenide with a potentiostatic sensor. A calibration for use in the calibration curve method, comprising a step of obtaining a measurement value, and a step of analyzing the tetravalent selenium concentration of the analytical sample by the calibration curve method based on the measurement value Is prepared based on the correlation between the tetravalent selenium concentration obtained in advance from a plurality of standard samples having known tetravalent selenium concentrations and the measured value of the potentiostatic electrolytic sensor. Analysis method.   The method for quantitative analysis of selenium according to claim 1 or 2, wherein nitric acid is added to the acid analysis sample to which sulfuric acid has been added as the acid, and this is heated to produce white smoke.   Nitric acid is added to the acid analysis sample to which sulfuric acid has been added as the acid, and this is heated to produce sulfuric acid white smoke, and then hydrochloric acid is added to adjust the acidity of the sulfuric acid and the acid by the hydrochloric acid. The method for quantitative analysis of selenium according to claim 1 or 2, wherein 4.0 to 6.7 N / L.   Sealing the sample for acid analysis in which at least one of hydrochloric acid and sulfuric acid is added to the sample for analysis in which tetravalent selenium is dissolved and the normality of the acid is adjusted to 0.13 to 6.7 N / L A container having a structure, means for adding sodium tetrahydroborate at a rate of 5 g / min or less to 1 L of the sample for acid analysis, a potentiostatic sensor for measuring hydrogen selenide and outputting a measurement value, and the acid A supply means for sucking the hydrogen selenide generated from the sample for analysis at 10 to 20 mL / min and supplying the hydrogen selenide to the constant potential electrolytic sensor, and a tetravalent obtained in advance from a plurality of standard samples having known tetravalent selenium concentrations. An analyzer having a calibration curve created based on the correlation between the selenium concentration and the measured value of the potentiostatic electrolytic sensor and analyzing the tetravalent selenium concentration of the analytical sample from the measured value based on the calibration curve Quantitative analysis system in which selenium to include and.   Sealing the sample for acid analysis in which at least one of hydrochloric acid and sulfuric acid is added to the sample for analysis in which tetravalent selenium is dissolved and the normality of the acid is adjusted to 0.13 to 6.7 N / L A container having a structure; means for adding sodium tetrahydroborate at a rate of 5 to 10 g / min to 1 L of the acidic analysis sample; means for supplying a carrier gas to the container at a rate of 500 to 700 mL / min; and hydrogen selenide A constant potential electrolytic sensor that measures the pressure and outputs the measured value; and the hydrogen selenide generated from the acidic analysis sample is sucked together with the carrier gas at 400 to 600 mL / min and supplied to the constant potential electrolytic sensor Calibration based on correlation between tetravalent selenium concentration obtained in advance from a plurality of standard samples with known tetravalent selenium concentrations and measured values of the potentiostatic sensor Quantitative analysis system in which selenium those comprising analyzing means for analyzing tetravalent selenium concentration of the sample for analysis from the measured values based on the calibration curve which has a.   The selenium quantitative analysis system according to claim 5 or 6, wherein nitric acid addition means for adding nitric acid to the acidic analysis sample to which sulfuric acid has been added as the acid, and heating the acidic analysis sample to which the nitric acid has been added And a selenium quantitative analysis system, further comprising a heating device that generates sulfuric acid white smoke. The selenium quantitative analysis system according to claim 5 or 6, wherein nitric acid addition means for adding nitric acid to the acidic analysis sample to which sulfuric acid has been added as the acid, and heating the acidic analysis sample to which the nitric acid has been added And a heating device for generating sulfuric acid white smoke, and hydrochloric acid is added to the sample for acid analysis after being heated by the heating device, so that the normality of the acid by the sulfuric acid and the hydrochloric acid is 4.0 to 6.7 N. A selenium quantitative analysis system, further comprising a hydrochloric acid addition means of / L.