JP4571052B2 - A method for collecting and analyzing trace amounts of arsenic in gases - Google Patents

Description

  The present invention relates to a method for collecting a total amount of trace arsenic (arsenic) in a gas and a method for analyzing the total amount, and more particularly, a method for collecting the total amount of trace arsenic compounds in a gas such as fuel gas, exhaust gas, or air, and It relates to a method for analyzing the total amount.

  Arsenic exists universally in nature. The crust and soil contain an average of about 5 ppm as an inorganic arsenic compound in the form of sulfides and oxides, the river water contains about 1 to 30 ppm as an inorganic arsenic compound, and the seawater contains inorganic arsenic compounds and organic arsenic. The total amount of the compound is about 2 ppm on average. Arsenic is also present in a small amount in the biosphere, and it is known that marine organisms contain higher concentrations of organic arsenic compounds than terrestrial organisms.

  In addition, it is known that arsenic compounds are also contained in dust particles in exhaust gas generated during combustion of fossil fuels, refining of various metals, and incineration of garbage. Arsenic compounds in the exhaust gas are mainly volatile arsenides, that is, metal compounds, but also include volatile arsenic oxides such as diarsenic trioxide.

In addition, the atmosphere contains arsenic compounds derived from these natural worlds, such as soil rolling up and artificial sources such as exhaust gas. According to the results data of the Ministry of the Environment in 2003, It is reported that an average of 1.7 ng / m ³ of arsenic compound is present.

  By the way, in the field of environmental quality such as exhaust gas and air and the field of gas quality control such as fuel gas, it is necessary to measure and grasp the presence or absence of arsenic in the gas. As a measurement method that can be used as a reference when analyzing arsenic, arsenic measurement in exhaust gas defined by JIS K 0083 (1997) (Non-patent Document 1) and arsenic in the atmosphere indicated by the Ministry of the Environment (Former Environment Agency) There exists a measuring method (nonpatent literature 2).

JIS K 0083 (1997) Environment Agency “Toxic Air Pollutant Measurement Method Manual (February 1997)”

Among them, a method for measuring arsenic in exhaust gas (hereinafter referred to as “JIS method” as appropriate) uses a gas to be measured as an absorption liquid (potassium permanganate aqueous solution, referred to as “KMnO ₄ aqueous solution” in this specification as appropriate). It is a method of passing. Since this method uses an absorbing solution, the flow rate is slow (about 60 L / hr), so the amount of collected gas is small, and the atmospheric concentration level (1 ng / m ³ ) cannot be measured.

  On the other hand, the arsenic measurement method in the atmosphere (hereinafter referred to as the “Ministry of the Environment” as appropriate) is a method in which arsenic in the air is collected with a filter using a high volume sampler or low volume sampler and the amount is quantified. is there. According to this method, a large amount of atmospheric arsenic can be measured by collecting a large amount of soot and dust by collecting a large amount of dust by flowing a large amount of air for a long time. However, this method quantifies only the arsenic compound contained in the particulate matter collected by the filter, and cannot quantitate the gaseous arsenic compound or the arsenic compound in the ultrafine particles that cannot be collected by the filter.

As described above, the JIS method cannot measure the atmospheric concentration level (1 ng / m ³ ) because the amount of collected gas is small. On the other hand, the Ministry of the Environment method cannot collect gaseous arsenic compounds and cannot collect arsenic compounds in ultrafine particles, so it cannot be said that the total amount of arsenic contained in the atmosphere is grasped.

  In general, most of the arsenic existing in the atmosphere is an oxide, which is a particulate matter. Arsenic oxide is not only in the form of particles, but also may be contained in particles such as dust. However, how much arsenic oxide is contained in how much particulate matter, especially how much arsenic compound is present in the fine particles of PM2.5 (= particulate matter having a particle size of 2.5 μm or less). There is no knowledge about whether or not.

Furthermore, there is a possibility that a gaseous arsenic compound is present in an environmental gas such as the atmosphere or exhaust gas, or an industrial gas such as fuel gas. In these gases, although not trapped by the PTFE filter having a filter pore diameter of 1 μm, the trapped case is trapped by the KMnO ₄ aqueous solution.

Under such circumstances, the arsenic collection method and the pretreatment method of the collected arsenic are still being studied. As part of this, the present inventors can also collect gaseous arsenic compounds in gases and arsenic compounds in ultrafine particles, which cannot be collected by the Ministry of the Environment method using a PTFE filter or the like, and have a higher flow rate than the Ministry of the Environment method. We aimed to develop a method that can collect at 1 m ³ / hr or more.

  Here, not limited to arsenic, in general, the lower limit of quantification in the case of measuring trace components is (a) concentration by collecting trace components, (b) pretreatment of the collected sample, (c) sensitivity of the measuring device. It depends on the synergistic effect of the three factors of improvement. Therefore, (a) for concentration by collecting trace components, the arsenic compound and the gaseous arsenic compound in the fine particles contained in the gas can be collected at a large flow rate, (b) the sample collected and collected. As for pretreatment, pretreatment from sample decomposition to quantification prevents contamination from the current method and makes it highly accurate. (C) For the improvement of the sensitivity of the measuring device, the current measurement method is more Three conditions and problems of measurement method for high sensitivity were examined.

  Then, through a verification test, we cleared each of these issues, developed a collection material that can collect gaseous arsenic compounds, particulate arsenic compounds, and arsenic compounds contained in the gas. By studying the high sensitivity measurement method including the pretreatment method of the collected sample, a method satisfying the above conditions (a) to (c) could be developed.

  That is, the present invention provides a method for collecting the total amount of gaseous arsenic compound, fine arsenic compound, and arsenic compound contained in the gas, and enables measurement of the arsenic concentration at the atmospheric level. The object of the present invention is to provide a method for analyzing the total amount of trace arsenic in a gas.

The present invention (1) is a method for collecting all trace amounts of arsenic in a gas. Then, when collecting and analyzing trace arsenic compounds in the gas, the gaseous arsenic compound in the gas, the fine arsenic compound, and the arsenic compound in the fine particles are collected by a glass fiber filter supporting KMnO _4. Features.

The present invention (2) is a method for collecting all trace amounts of arsenic in a gas. When collecting and analyzing trace arsenic compounds in the gas, the gaseous arsenic compound, the fine arsenic compound in the gas, and the arsenic compound in the fine particles are captured by a glass fiber filter and fluororesin filter carrying KMnO _4. It is characterized by collecting.

The present invention (3) is a method for collecting all trace amounts of arsenic in a gas. When collecting and analyzing a trace amount of arsenic compound in the gas, the gaseous arsenic compound, the particulate arsenic compound, and the arsenic compound in the fine particle are composed of a glass fiber filter and a fluororesin filter carrying KMnO _4. It is characterized by collecting the collecting units in a plurality of stages. As will be described later, a two-stage (that is, two-stage) collection unit is sufficient, but three or more stages (three-stage) may be arranged as necessary.

The present invention (4) is a method for analyzing the total amount of trace arsenic in a gas. And, when collecting and analyzing a trace amount of arsenic compound in the gas, after collecting the gaseous arsenic compound in the gas, the fine arsenic compound, and the arsenic compound in the fine particle with a glass fiber filter carrying KMnO ₄ , The arsenic compound in the KMnO ₄ -supported glass fiber filter is acid-decomposed, and then the acid-decomposed aqueous solution is sequentially concentrated by the following operations (a) to (e) to increase the concentration of the aqueous solution. And
(A) KMnO ₄ aqueous solution is added to the acid decomposition aqueous solution.
Ammonia water is added to the aqueous solution obtained in (b) and (a) to adjust the pH to 7-8.
An aqueous solution of hydroxylammonium chloride as a reducing agent is dropped into the aqueous solution of (c) and (b), and the arsenic compound is transferred to the product precipitation side.
The precipitates of (d) and (c) are filtered to collect the residue.
An excess aqueous solution of hydroxylammonium chloride is added to the residue of (e) and (d) to dissolve the residue, and an acid and a reducing agent are added.

The present invention (5) is a total amount analysis method for trace amounts of arsenic in gas. When collecting and analyzing trace arsenic compounds in the gas, the gaseous arsenic compound, the fine arsenic compound in the gas, and the arsenic compound in the fine particles are captured by a glass fiber filter and fluororesin filter carrying KMnO _4. After collecting, the arsenic compounds in the KMnO ₄ -supported glass fiber filter and fluororesin filter are acid-decomposed, and then the acid-decomposed aqueous solutions are sequentially added to the following (a) to (e) in order to increase the concentration of the aqueous solution. It is characterized by concentrating by the operation.
(A) KMnO ₄ aqueous solution is added to the acid decomposition aqueous solution.
Ammonia water is added to the aqueous solution obtained in (b) and (a) to adjust the pH to 7-8.
An aqueous solution of hydroxylammonium chloride as a reducing agent is dropped into the aqueous solution of (c) and (b), and the arsenic compound is transferred to the product precipitation side.
The precipitates of (d) and (c) are filtered to collect the residue.
An excess aqueous solution of hydroxylammonium chloride is added to the residue of (e) and (d) to dissolve the residue, and an acid and a reducing agent are added.

According to the present invention (1) to (5), the total amount of gaseous arsenic compound, particulate arsenic compound, and arsenic compound in fine particles is captured and collected by the glass fiber filter carrying KMnO _4. It can be collected by changing to oxide by reaction with ₄ . Further, as in the present inventions (2), (3), and (5), a fine particle arsenic compound such as arsenic dioxide and arsenic trioxide can be obtained by disposing a fluororesin filter behind the KMnO ₄ -supported glass fiber filter. The arsenic compound in the fine particles can be collected more completely.

According to the present invention, by collecting and analyzing the total amount of trace amounts of arsenic compounds in gas such as air, exhaust gas, or fuel gas, the arsenic concentration at the atmospheric level (= the lower limit of measurement quantification is 50 m ³ gas sampling) Measurement of 1 ng / m ³ ) is possible. The present invention can be used for investigation of arsenic in gas in environment-related fields such as exhaust gas and air, and investigation of arsenic in gas in quality control fields such as fuel gas. In the present invention, the particulate arsenic compound in the gas and the arsenic compound in the fine particle are also collected, but there is no upper limit and lower limit in the size of the fine particle, and so-called ultrafine particles are included.

In the present invention, a glass fiber filter loaded with KMnO ₄ (hereinafter referred to as appropriate) is used as a trapping material for gaseous arsenic compounds, fine arsenic compounds in fine gases and arsenic compounds in fine particles, such as air, exhaust gas, or fuel gas. It is important to use “KMnO ₄ glass fiber filter”). This filter is constituted by impregnating glass fiber with KMnO ₄ aqueous solution and drying it, thereby supporting KMnO ₄ on the glass fiber. With this collection material, gaseous arsenic compounds, particulate arsenic compounds, and arsenic compounds in fine particles can be collected very effectively in the gas such as air, exhaust gas, or fuel gas.

  Japanese Patent No. 3471446 discloses that metal impurities contained in a process gas in a semiconductor manufacturing process are collected by a porous body made of porous glass which is a strong acid resistant material. However, the porous body made of the porous glass is different from the glass fiber in the production method, shape, structure, and characteristics (Non-patent Document 3), and the metal impurities that are collected in the same publication are specifically: Fe, Al, Mn, Ni, Cu, Zn, Cr, or a compound thereof, and does not capture arsenic or arsenic compounds.

Japanese Patent No. 3471446 “Ceramic Engineering Handbook” published on April 10, 1989, p. 1150-1155, p. 1188-1190

  Hereinafter, the present invention will be described in order, including the process leading up to the development of the present invention.

<KMnO ₄ aqueous solution method: JIS method>
FIG. 1 shows a sampling device for an arsenic analysis method in exhaust gas defined by the JIS method, that is, JIS K 0083 (1997). Exhaust gas flowing through the duct is passed through two absorption bottles arranged in the cooling tank while being kept warm and heated as necessary to avoid moisture condensation, and then discharged through a glass filter, drying tube, etc. The The exhaust gas flowing through the duct is sucked by a vacuum pump.

Each absorption bottle contains 50 mL of KMnO ₄ aqueous solution (100 mL by dissolving 0.5 g of KMnO ₄ in water) specified in JIS K 8247 as an absorbing solution for gaseous arsenic compounds such as arsenic hydride. And hold at 0-10 ° C. in a cooling bath.

<Filter method: Ministry of the Environment Act>
In accordance with the Ministry of the Environment Act, namely, the Environmental Agency's “Manual for Measuring Methods for Hazardous Air Pollutants (February 1997), Chapter IV Method for Measuring Nickel and Arsenic in the Air”, a high volume air sampler is used to remove airborne dust. Use to collect on filter. All particles are collected without using a sizing device, and the collected sample is subjected to arsenic analysis. This sampling apparatus has a structure shown in FIG. As shown in FIG. 2 (a), the apparatus includes a filter holder A, a pump B, and a flow rate measuring unit C, which are housed and arranged in a protective case.

  The filter holder A includes window-side frames 2 and 7 holding a collection filter 4 and a funnel-shaped portion 1. As shown in FIG. 2 (b), the collection filter 4 is disposed on a stainless steel wire mesh 3 supported by a frame 2 connected to the funnel-shaped portion 1. In FIG. 2B, 5 is a fluororesin tape, 6 is a packing, and 8 is a fastener. According to the Ministry of the Environment, it is said that a quartz fiber filter, a fluororesin filter, a nitrocellulose filter, etc. are used as the collection filter 4, but a PTFE filter which is a kind of fluororesin is used in this experiment. did.

<Method according to the present invention: KMnO ₄ glass fiber filter method>
FIG. 3 shows a sampling device used for collecting arsenic compounds according to the present invention. As shown in FIG. 3, a two-stage (namely, two-stage) KMnO ₄ glass fiber filter and a dry gas meter were disposed in the sample gas line in sequence. In addition, each KMnO ₄ glass fiber filter was configured by sequentially arranging a SUS304 holder, PTFE packing, a KMnO ₄ glass fiber filter, a PTFE filter, a SUS304 support plate, and a SUS304 holder in a gastight manner.

Among them, KMnO ₄ glass fiber filters, glass fiber filter paper (thickness = 0.74 mm, diameter = 47 mm, trade name = GA-200) to, and impregnated with KMnO ₄ aqueous solution, the KMnO ₄ to the glass fiber by drying It is supported.

In the sampling apparatus, although arranged respectively PTFE filter downstream of KMnO ₄ glass fiber filter in the subsequent stage and two-stage KMnO ₄ glass fiber filters in the first stage, PTFE filter, particulate arsenic contained in the gas Even when only a small part of the arsenic compound in the compound and fine particles could not be captured by the KMnO ₄ glass fiber filter, it is for capturing them more perfectly.

The collection test of the arsenic compound in the sample gas was performed by the above three methods. This sample gas generates arsenic hydride (arsine: AsH ₃ , boiling point = −55 ° C.) from a standard arsenic sample using a hydride generator, and this is generated in Ar gas at about 1.5 μg / m ³ ( Arsenic equivalent). The reason why the arsenic hydride concentration is set to such a high concentration is to facilitate comparison of the results of the three methods. The collection test was conducted through 3 m ³ sample gas at each flow rate in all three methods.

<Pretreatment method of collected sample: acid decomposition>
The collected sample was pretreated. The pretreatment method is a treatment prior to quantification by ICP spectroscopy (inductively coupled high-frequency plasma spectroscopy, hereinafter referred to as “ICP method”). A method of completely decomposing (arsenic compound) using nitric acid and sulfuric acid was applied. The collected sample subjected to the pretreatment is a KMnO ₄ aqueous solution in two absorption bottles in the JIS method, a PTFE filter in the Ministry of the Environment method, and a double KMnO ₄ glass fiber filter in the method of the present invention.

In the method of the present invention, a PTFE filter is disposed at each subsequent stage of the double KMnO ₄ glass fiber filter. However, the PTFE filter is effective for collecting particulate arsenic compounds and arsenic compounds in the particles. However, arsenic hydride and the like based on the test results of the Ministry of the Environment using only the PTFE filter (see Table 2 below). The arsenic compound is not collected and has no effect on the presence or absence of the collection effect of the KMnO ₄ glass fiber filter. In the method for analyzing the total amount of trace arsenic in the gas of the present invention, when a PTFE filter is disposed after the KMnO ₄ glass fiber filter to collect an arsenic compound, it is a matter of course that pretreatment including the PTFE filter is performed. .

  The nitric acid used for the acid decomposition is an obstacle when arsenic is quantified by ICP method or atomic absorption photometry. For this reason, after making arsenic hydride into aqueous solution, the operation which drives out nitric acid is required. For the purge operation, the Kjeldahl decomposition method, that is, a Kjeldahl flask was used to determine that the best solution was to make the undissolved solution into an aqueous solution while heating and to carry out the work of flushing nitric acid consistently. Table 1 summarizes the test conditions up to the pretreatment. In Table 1, “%” is “wt%”, and this is the same in Table 4, Table 6, and Table 8 described later.

The arsenic hydride concentration was measured by ICP method for each sample gas after the pretreatment. An ICP device (= ICP spectroscopic analyzer) manufactured by Perkin Elma was used as the analyzer. The measurement results for each collection flow rate in the three methods are shown in Table 2. In Table 2, “arsenic concentration (μg / m ³ )” is a value obtained by converting the arsenic hydride concentration into an arsenic (element) concentration. This also applies to Table 7 described later.

As shown in Table 2, the Ministry of the Environment uses only a PTFE filter, but the arsenic concentration in this method is less than 0.01 μg / m ³ , which is almost ineffective, and the PTFE filter is a gaseous arsenic compound. It shows that there is no arsenic hydride collection effect. In the JIS method, but using a KMnO ₄ aqueous solution, and a flow rate of 0.8 L / min at 1.3 ug / m ^3, a flow rate of 2.2 L / min at 1.5 [mu] g / m ^3, compared with the flow rate of 0.8 L / min And improve a little. However, at a flow rate of 2.3 L / min, it becomes 1.3 μg / m ³ , indicating that the effect of collecting arsenic hydride does not improve even if the flow rate is increased further.

In contrast, the arsenic concentration according to the method of the present invention is relatively higher than the arsenic concentration of the JIS method using an aqueous KMnO ₄ solution, and a better collection effect is shown by increasing the collection flow rate. That is, according to the present invention method, a flow rate of 2.0L / min at 1.2 ug / m ^3, and improved 1.6 [mu] g / m ³ at a flow rate of 4.5 L / min, a flow rate of 9.0 L / min at 1 .9μg / m ^3, and the shows the values of 1.7μg / m ³ even flow rate 12.0 L / min.

<Examination of concentration method of acid decomposition aqueous solution>
Here, in the normal pretreatment method based on the pretreatment method, that is, the JIS method, the amount of the aqueous solution is 50 mL or more due to a washing operation during the acid decomposition operation, and the aqueous solution is diluted. Therefore, in order to increase the concentration of the aqueous solution, a method for producing and concentrating a precipitate of an arsenic compound in the acid-decomposed aqueous solution based on the following procedures (a) to (e) was studied.
(A) KMnO ₄ aqueous solution is added to the acid decomposition aqueous solution.
Ammonia water is added to the aqueous solution obtained in (b) and (a), and pH is adjusted to 7-8.
A hydroxylammonium chloride aqueous solution as a reducing agent is dropped into the aqueous solution of (c) and (b) to form a precipitate (arsenic compound is transferred to the precipitation side).
Filter the precipitates (d) and (c) and collect the residue.
Add excess hydroxylammonium chloride aqueous solution to the residue of (e), (d) to dissolve the residue, then add acid and reducing agent to make 10 mL. Here, sulfuric acid was used as the acid, and hydrochloric acid, potassium iodide and L-ascorbic acid were used as the reducing agent.

An aqueous solution containing a certain amount of arsenic (100 μg: arsenic conversion) was produced with an arsenic standard reagent.
(A) About this aqueous solution, concentration operation as said (a)-(e) was implemented, the arsenic density | concentration in a residue was measured, and the concentration efficiency to the residue side of arsenic was investigated.
(B) Further, in order to investigate the effect of neutralization with ammonia water in the operation of (b), an operation of generating and concentrating a precipitate without adding ammonia water, measuring the arsenic concentration in the residue, The concentration efficiency to the residue side was investigated.
(C) Further, instead of adjusting the pH to 7 to 8 by the operation of (b), an excess ammonia water is added to form a precipitate, and the concentration is performed without adding the hydroxylammonium chloride aqueous solution. The arsenic concentration in the residue was measured, and the concentration efficiency of arsenic on the residue side was examined.

  In any of these cases (A) to (C), the amount of the aqueous solution is 10 mL with respect to 50 mL in the pretreatment method, and is concentrated five times. Table 3 shows these results.

  As shown in Table 3, arsenic is concentrated almost 100% to the residue side in the concentration operation as shown in (A), that is, the above-described (a) to (e).

  On the other hand, in the concentration operation of (B), the concentration rate to the residue side is inferior to the concentration operation of (A). There was variation for each test of 4 to 6, and in the concentration operation of (C), the concentration rate to the residue side was about 91% at the maximum, and the concentration rate also varied and was not stable. As a cause of these, when neutralization operation is not performed as in (B), there is an operational problem that the precipitated particles are small and difficult to filter, and in the case of precipitation formation due to excess ammonia water in (C) It is considered that there is a problem that the rate of precipitate formation is slow and the precipitate is not sufficiently formed.

From the above results, among the above (A), that is, (a) to (e), ammonia water was added to an aqueous solution obtained by adding an aqueous KMnO ₄ solution to an acid decomposition aqueous solution as in (a) to (b), and pH It is important to adjust the acid decomposition aqueous solution to 7 to 8, and the acid decomposition aqueous solution is converted into a normal (ie, compliant with JIS method) by the concentration operation (a) to (e) including the operations (a) to (b). It was found that it can be concentrated 5 times as much as the pretreatment method (with normal specifications).

<Measurement test of arsenic: ICP method>
Based on the above results from the collection of arsenic compounds to the acid decomposition operation and the concentration operation, an arsenic measurement test by the ICP method was carried out. As in the above test, an ICP device manufactured by Perkin Elma was used as the analyzer. Table 4 shows the conditions for generating arsenic hydride (hydride), which is a gaseous arsenic compound used in the ICP apparatus.

As shown in Table 4, the concentrations of the individual hydride generating reagents at the time of measurement, that is, sodium tetrahydroborate and hydrochloric acid (HCL) were set to 5 times the normal concentration based on the above findings, and the ICP device By changing the inner diameter of the sample introduction pump tube, the sample introduction amount was reduced to 1/5 of the normal amount. Under these conditions, arsenic was continuously measured. FIG. 4 summarizes the steps of collection, acid decomposition, concentration (from addition of KMnO ₄ aqueous solution to constant volume), arsenic hydride generation, and measurement in this arsenic measurement test.

  FIG. 5 shows the luminescence intensity in the case of introducing the hydride generating reagent of the normal specification, and FIG. 6 shows the luminescence intensity in the case of introducing the hydride generating reagent having a concentration five times that of the normal specification. 5 to 6 are data measured without generating arsenic hydride and correspond to a so-called blank test. This is the same for “● 0 ppm” in FIG.

  As shown in FIG. 5, the emission intensity when generated by a normal reagent is about 480 (au), whereas as shown in FIG. 6, the emission intensity when generated by a 5-fold concentration reagent is about 2500 (a .u.). Thus, the emission intensity at the same concentration can be increased by about 5.5 times without impairing the stability of the plasma. That is, by generating hydride from a 5-fold concentration reagent, the measurement sensitivity can be improved 5 times under the same measurement conditions. In this experiment, the acid-decomposed aqueous solution was concentrated 5 times as usual, but by concentrating it to 4 to 6 times, the measurement sensitivity can be improved corresponding to the concentration under the same measurement conditions.

  In addition, in the quantification by the ICP device at the time of generation from the normal hydride generating reagent, the instantaneous luminescence intensity is measured, but as part of the examination of the sample introduction method, the luminescence intensity is continuously increased during the sample introduction. It has become clear that data can be detected easily and data reproducibility can be obtained. Thus, by continuously detecting the emission intensity and accumulating the emission intensity, it is possible to perform quantitative determination with further improved sensitivity and accuracy.

<Test conducted with a cushion tank prior to sample introduction into the ICP device>
In the above experiment, a mixed gas of Ar gas and arsenic hydride gas from a hydride generator was introduced into the ICP device as a sample. On the other hand, a cushion tank (absorption bottle: 250 mL dresser) was provided between the hydride generator and the ICP spectroscopic analyzer and tested in the same manner as described above. FIG. 7 is a test result in the case where a cushion tank is provided for arsenic hydride gas generated by a hydride generating reagent having a concentration five times that of normal specifications.

  As shown in FIG. 7, the introduction gas (mixed gas of Ar gas and generated arsenic hydride gas) from the hydride generator to the ICP device is passed through the cushion tank before being introduced into the ICP device, so that The concentration of arsenic hydride in the introduced gas is made uniform, and variations in measurement intensity can be reduced.

  That is, as shown in FIG. 6, the luminescence intensity of the arsenic hydride gas generated by using a normal 5-fold concentration reagent is as high as about 2500 (au), but the intensity varies. On the other hand, as shown in FIG. 7, by providing a cushion tank, the introduction flow rate of arsenic hydride to the ICP device can be stabilized, and the variation in measurement intensity can be reduced.

  FIG. 8 is a graph showing the integrated value of the emission intensity with respect to the concentration based on the data of FIG. As shown in FIG. 8, the integrated value is 0, 1, 5, 10, 20 μg / L, and the correlation of five points including zero is linear, that is, first order. As described above, it is shown that, by setting the arsenic hydride generating reagent concentration to 5 times the normal concentration and providing a cushion tank, stable measurement is possible as a straight line is drawn up to 1 ppb level.

As a result, the actual lower limit of quantification can be measured to a concentration lower than 1 μg / L. However, if a KMnO ₄ glass fiber filter, acid decomposition operation, and reagents are included, there is not much meaning to pursue further sensitivity. However, it is considered sufficient that the 1 μg / L level can be accurately obtained as in the method of the present invention.

<High-speed collection test using KMnO ₄ glass fiber filter>
A high-speed collection test was conducted using a glass fiber filter carrying KMnO ₄ . FIG. 9 is a schematic of the apparatus used to collect gaseous arsenic (arsenic hydride) in this experiment. Using this apparatus, arsenic hydride was passed through a glass fiber filter carrying KMnO _{4 in} duplicate (that is, two stages) at a flow rate of 25 L / min. And glass having KMnO ₄ carried in duplicate at a flow rate of 50 L / min. And passed through a fiber filter. Table 5 shows the results. In Table 5, the value in the “flow velocity” column is an actual measurement value.

As shown in Table 5, in the collection at a flow rate of 25 L / min, almost the first stage is collected, but the second stage is not collected. On the other hand, in the collection at a flow rate of 50 L / min, about 16% of the arsenic hydride was collected and detected in the second stage. This, KMnO ₄ loaded glass fiber filter with the collected hydrogenated arsenic is was understood by reaction with KMnO ₄ supported on glass fiber filters are adsorbed, the filter passage speed is fast, It shows that it cannot fully react with KMnO ₄ . However, from the above fact, the atmospheric level can be measured by increasing the amount of collected gas. Moreover, by using a two-stage glass fiber filter carrying KMnO ₄ , it is possible to collect more than 80% of arsenic hydride in the first stage, and recover the amount of arsenic hydride that passes through the second stage. Considering that the efficiency is required, it is understood that there is no problem in the collection with a flow rate of 50 L / min and a two-stage method (two-unit method).

<Carrying test of arsenic in the atmosphere by the Ministry of the Environment and the present method>
The collection test of the arsenic compound in the atmosphere by the Ministry of the Environment method using a PTFE filter and the method of the present invention using a glass fiber filter carrying KMnO ₄ was carried out. In the Ministry of the Environment method, the apparatus of FIG. 2 was used, and in the method of the present invention, the apparatus of FIG. 3 was used. The test conditions are as shown in Table 6, and Table 7 shows the test results. From this result, it was found that the samples in this practical test did not contain gaseous, fine particles, and arsenic compounds in the fine particles.

Based on the above results, the preferred method of collecting and analyzing the total amount of trace arsenic in gas using the present invention, that is, “sampling (= glass fiber filter carrying KMnO ₄ + PTFE filter, arsenic compound in gas Table 8 shows an example of the process of “collection of sample) → acid decomposition / solution of collected sample (= pretreatment of collected sample) → analysis / quantification of pretreated sample by ICP method”.

Diagram showing a sampling device for sampling arsenic compounds in exhaust gas by JIS method Arrangement sampling device for atmospheric arsenic compounds by the Ministry of the Environment The figure which shows the sampling device for arsenic compound collection by this invention method A diagram summarizing the steps of arsenic compound collection, acid decomposition, concentration, and measurement Diagram showing results for normal hydride generation reagent amounts The figure which shows the result in the case of 5 times the amount of hydride generating reagents The figure which shows the test result about the hydrogenation generation reagent 5 times solution before cushion tank installation The figure which shows the test result about the hydrogenation generation reagent 5 times solution after cushion tank installation The figure which shows the apparatus for arsenic hydride collection used in <High-speed collection test using KMnO ₄ glass fiber filter>

Explanation of symbols

A Filter holder B Pump C Flow rate measuring part 1 Stainless steel mesh 2, 7 Window side frame 3 Funnel-shaped part 4 Collection filter 5 Fluororesin tape 6 Packing 8 Fastening tool

Claims (4)

When collecting and analyzing trace arsenic compounds in a gas, the gaseous arsenic compound, the fine arsenic compound in the gas, and the arsenic compound in the fine particle are collected by a glass fiber filter and a fluororesin filter carrying KMnO _4. A method for collecting a total amount of trace amount of arsenic in a gas. When collecting and analyzing trace arsenic compounds in a gas, the gas arsenic compound in the gas, the fine arsenic compound, and the arsenic compound in the fine particles are collected from a glass fiber filter and a fluororesin filter carrying KMnO _4. A method for collecting a total amount of trace arsenic in a gas, characterized in that the unit is arranged in a plurality of stages and collected. A method for collecting and analyzing a trace amount of arsenic compound in a gas, wherein a gaseous arsenic compound, a particulate arsenic compound and an arsenic compound in a fine particle are separated by a glass fiber filter and a fluororesin filter supporting KMnO _4. After the collection, the KMnO ₄ -supported glass fiber filter and the arsenic compound in the fluororesin filter are acid-decomposed, and then the acid-decomposed aqueous solutions are sequentially added to the following (a) to (e The method for analyzing the total amount of trace arsenic in the gas, characterized in that it is concentrated by the operation of
(A) KMnO ₄ aqueous solution is added to the acid decomposition aqueous solution.
Ammonia water is added to the aqueous solution obtained in (b) and (a) to adjust the pH to 7-8.
An aqueous solution of hydroxylammonium chloride as a reducing agent is dropped into the aqueous solution of (c) and (b), and the arsenic compound is transferred to the product precipitation side.
The precipitates of (d) and (c) are filtered to collect the residue.
An excess aqueous solution of hydroxylammonium chloride is added to the residue of (e) and (d) to dissolve the residue, and an acid and a reducing agent are added. 4. The method for analyzing the total amount of trace arsenic in gas according to claim 3 , wherein the acid decomposing reagent in the acid decomposition is sulfuric acid or nitric acid.

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