JP2013047659A - Quantity determination method of total nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the quantity of total nitrogen in examination water up to a high concentration area through simple operation by utilizing diazotization reaction caused by nitrite ion.SOLUTION: A quantity determination method of total nitrogen in examination water includes a step 1 of adding alkali metal salt of peroxodisulfate to the examination water and heating the examination water from 90°C to its boiling temperature under alkalinity, a step 2 of adding vanadium chloride (III) and a diazotization reagent which reacts with nitrite ion to generate diazonium salt to the examination water having undergone the step 1 and heating the examination water under acidity, and a step 3 of measuring a nitrite ion concentration by measuring absorbance of coloration by the diazotization reagent or absorbance of coloration by the generated diazonium salt for the examination water having undergone the step 2. A chemical compound selected from among an aromatic primary amine compound group having a keton group or a nitro group and a 3-amino-2-cyclohexene-1-one skeleton-containing compound group is used as the diazotization reagent.

Description

  The present invention relates to a method for quantifying total nitrogen, and more particularly to a method for quantifying total nitrogen in test water.

  Since nitrogen is one of the causative substances related to eutrophication such as marine water, lake water, river water, and groundwater, there are emission regulations for factory effluent. Prior to discharge, quantification of ionic nitrogen (for example, nitrate ions and nitrite ions) that is a nutrient source for ecosystems is required. However, factory effluents generally contain not only nitrogen in an ionic state but also nitrogen as various nitrogen compounds, and these nitrogen compounds are naturally decomposed after being discharged into the environment, resulting in an ionic state. Generate nitrogen. For this reason, factory wastewater and the like are often required to determine the total amount of nitrogen including ionic nitrogen that can be generated from nitrogen compounds, so-called total nitrogen.

  In one form of quantification of total nitrogen contained in inspection water such as factory effluent, the nitrogen compound contained in inspection water is converted to nitrate ion by oxidative decomposition, and then pretreated to convert it to nitrite ion, Nitrite ions contained in the test water after this pretreatment are quantified. And the total nitrogen concentration is calculated | required by converting the fixed_quantity | quantitative_assay result of nitrite ion.

  As a method for quantifying nitrite ions contained in test water, a method using a diazotization reaction with nitrite ions is known, and such a method is specified in the Japanese Industrial Standards (JIS) as an official method. A naphthylethylenediamine absorptiometric method is known (Non-patent Document 1). This quantification method (hereinafter referred to as JIS method) is a azo compound produced by coupling a diazonium salt produced by reaction of nitrite ions contained in test water with sulfanilamide under acidic conditions with naphthylethylenediamine. Nitrite ions are quantified by measuring the coloration (coloration) of the test water by means of absorptiometry.

However, the JIS method is very sensitive to coloring of the test water by the azo compound produced, and the coloring intensity (molar extinction coefficient) is too high, so it is difficult to accurately quantify high concentration of nitrite ions in the test water. The measurable range of the nitrite ion concentration is limited to 0.06 to 0.6 mg [NO ₂ ⁻ ] / L. Since the nitrite ion concentration in this range is a very small range of about 0.02 to 0.2 mg [N] / L in terms of total nitrogen, the JIS method is difficult to apply to the determination of total nitrogen. .

In Patent Document 1, as a method for quantifying nitrite ion instead of JIS method, a porphyrin compound having an amino group in a porphine nucleus is added to test water, and a diazo group generated by reaction of the porphyrin compound and nitrite ion is added. It describes a method for measuring the absorbance of the porphyrin compound possessed or the fluorescence intensity upon excitation. This method is based on the fact that the sole absorption band of the porphyrin compound decreases due to the formation of a diazo group, and the only reaction required is the reaction between the porphyrin compound and nitrite ion. Nitrite ions can be quantified with a simple operation compared to the JIS method, which requires a two-step reaction with a ring reaction. However, according to the description of Patent Document 1 (particularly, paragraph 0023), this quantification method has a measurable range of nitrite ion concentration of about 0 to 0.018 mg [NO ₂ ⁻ ] / L. Since the ion concentration is only a minute range of about 0 to 0.006 mg [N] / L in terms of total nitrogen, it is difficult to apply to the determination of total nitrogen as in the JIS method. Moreover, according to the description of Patent Document 1 (particularly, paragraph 0023 and FIG. 4), this quantification method is more than twice the molar equivalent of nitrite ions contained in test water in order to produce a porphyrin compound having a diazo group. This is uneconomical because it is necessary to use a large amount of the porphyrin compound, and it is difficult to reduce the size of the apparatus in order to realize an automated quantitative apparatus.

Japanese Industrial Standard JIS K 0102, Factory Wastewater Test Method (2008) 43.1.1

Japanese Patent Laid-Open No. 9-89781 (Claims, paragraphs 0012, 0016 and 0023 and FIG. 4 etc.)

  An object of the present invention is to use a diazotization reaction with nitrite ions, so that the total nitrogen of test water can be quantified to a high concentration region by a simple operation.

  The present invention relates to a method for quantifying the total nitrogen of test water. This method comprises adding a peroxodisulfuric acid alkali metal salt to test water and heating it under alkalinity, and a test through step 1 Step 2 in which vanadium (III) chloride and a diazotizing reagent capable of producing a diazonium salt by reaction with nitrite ion are added to water and heated in an acidic state. And step 3 of measuring the nitrite ion concentration by measuring at least one of the absorbance of the coloring due to the oxidizing reagent and the absorbance of the coloring due to the formed diazonium salt. In this method, a compound selected from the group consisting of an aromatic primary amine compound group having a ketone group or a nitro group and a 3-amino-2-cyclohexen-1-one skeleton-containing compound group is used as the diazotization reagent. .

  In step 1, for example, the inspection water is heated at a temperature from 90 ° C. to the boiling temperature.

  In one form of the quantification method of the present invention, for example, before the step 3, the method further includes a step of adjusting the pH of the test water that has passed through the step 2 to be higher than 7, and the coloring of the diazotizing reagent in the step 3 is performed. Measure absorbance.

  The aromatic primary amine compound group used in the present invention is usually a first group consisting of an aromatic primary amine compound having a ketone group or a nitro group in the ortho or para position, and a ketone group or And a second group of aromatic primary amine compounds having a nitro group. The first group includes, for example, 1-aminoanthraquinone, 2-nitroaniline, sodium 4-nitroaniline-2-sulfonate, p-nitroaniline, 2-amino-3-hydroxyanthraquinone and 1-amino-4-bromoanthraquinone. The second group consists of, for example, 3′-aminoacetophenone and 3-aminobenzophenone.

  On the other hand, the 3-amino-2-cyclohexen-1-one skeleton-containing compound group includes, for example, 3-amino-2-cyclohexen-1-one and 2-amino-3-chloro-1,4-naphthoquinone.

  In another embodiment of this quantification method, a diazotizing reagent is selected from the first group in step 2, and the color absorbance by the diazotizing reagent is measured in step 3. In this case, in Step 2, together with vanadium chloride (III) and a diazotizing reagent, at least one compound selected from the group consisting of alcohol compounds and hypophosphorous acid and salts thereof is further added to the test water. It is preferable to do this.

  In still another embodiment of this quantification method, a diazotizing reagent is selected from the second group in step 2, and the absorbance of coloring by the diazotizing reagent is measured in step 3.

  In still another embodiment of this quantification method, a diazotization reagent is selected from the group of compounds containing a 3-amino-2-cyclohexen-1-one skeleton in Step 2, and the absorbance of coloring by the diazotization reagent is determined in Step 3. taking measurement.

  In the quantification method of each of the above forms in which the absorbance of coloring by the diazotizing reagent is measured in Step 3, it is usually preferable to further include a step of adjusting the pH of the test water that has passed through Step 2 to be higher than 7.

  In still another embodiment of this quantification method, a diazotizing reagent is selected from the second group in Step 2, and the absorbance of coloring by the diazonium salt is measured in Step 3.

  Since the total nitrogen determination method according to the present invention includes the above-described steps, the total nitrogen of test water can be easily quantified to a high concentration region while utilizing a diazotization reaction with nitrite ions. Can do.

FIG. 3 is a graph showing the result of an absorption spectrum measured in Example 1. FIG. 3 is a diagram showing a calibration curve created in Example 1. FIG. 6 is a graph showing the result of an absorption spectrum measured in Example 2. FIG. 6 is a diagram showing a calibration curve created in Example 2. FIG. 6 is a graph showing the results of absorption spectra measured in Example 3. FIG. 6 is a diagram showing a calibration curve created in Example 3. FIG. 6 is a graph showing the result of an absorption spectrum measured in Example 4. The figure which shows the calibration curve created in Example 4. FIG. The figure which shows the result of the absorption spectrum measured by Reference Example 1A. The figure which shows the calibration curve created in Reference Example 1A. The figure which shows the result of the absorption spectrum measured by Reference Example 1B. The figure which shows the calibration curve created in Reference Example 1B. The figure which shows the result of the absorption spectrum measured by Reference Example 1C. The figure which shows the calibration curve created in Reference Example 1C. The figure which shows the result of the absorption spectrum measured by Reference Example 1D. The figure which shows the calibration curve created in Reference Example 1D. The figure which shows the calibration curve created in Reference Example 1E. The figure which shows the calibration curve created in Reference Example 1F. The figure which shows the calibration curve created in Reference Example 1G. The figure which shows the calibration curve created in Reference Example 1H. The figure which shows the calibration curve created in Reference Example 1I. The figure which shows the calibration curve created in Reference Example 1J. The figure which shows the calibration curve created in Reference Example 1K. The figure which shows the calibration curve created in Reference Example 1L. The figure which shows the result of the absorption spectrum measured by Reference Example 1M. The figure which shows the calibration curve created in Reference Example 1M. The figure which shows the result of the absorption spectrum measured by Reference Example 1N. The figure which shows the calibration curve created in Reference Example 1N. The figure which shows the calibration curve created in Reference Example 1O. The figure which shows the calibration curve created by the reference example 1P. The figure which shows the calibration curve created in Reference Example 1Q. The figure which shows the calibration curve created in Reference Example 1R. The figure which shows the calibration curve created in the comparative example 1. The figure which shows the result of the absorption spectrum measured by Reference Example 2A. The figure which shows the result of the absorption spectrum measured by Reference Example 2B. The figure which shows the result of the absorption spectrum measured by Reference Example 2C. The figure which shows the result of the absorption spectrum measured by Reference Example 2D. The figure which shows the result of the absorption spectrum measured by Reference Example 3A. The figure which shows the result of the absorption spectrum measured by Reference Example 3B. The figure which shows the result of the absorption spectrum measured by Reference Example 3C.

  The test water that can quantify the total nitrogen by the method of the present invention is not particularly limited, but usually drainage that is subject to nitrogen emission regulations such as factory effluent and domestic effluent, as well as marine water and lakes. Natural water such as water, river water and groundwater, which may contain nitrogen compounds. However, the quantification method of the present invention can also be applied to test water containing no nitrogen compound.

  When quantifying the total nitrogen of test water, first, a predetermined amount of test water is collected, and the nitrogen compound contained in the test water is oxidatively decomposed to convert nitrogen constituting the nitrogen compound into nitrate ions. For the pretreatment (step 1). In addition, the nitrite ion contained in test water from the beginning is oxidized together in this process, and once converted into nitrate ion. In addition, nitrate ions contained in the test water from the beginning are maintained as nitrate ions in this step.

  In this step, an alkali metal salt of peroxodisulfuric acid is used, and the nitrogen compound is oxidatively decomposed under alkalinity. The method using an alkali metal peroxodisulfate is, for example, in the “ultraviolet absorptiometric method” described in Japanese Industrial Standards JIS K0102 “Factory Wastewater Test Method (2008)” 45.2, converting nitrogen compounds to nitrate ions. It is described as a method for conversion and can be carried out according to this description. However, this “ultraviolet absorptiometric” method involves heating test water to which an alkali metal salt of peroxodisulfuric acid is added at 120 ° C. for 30 minutes under alkalinity. It is necessary to use a pressure resistant reactor. For this reason, this method has a problem because it leads to complication of the automation device when it is assumed that the quantification method of the present invention is automated.

  In view of this, it is preferable that the quantification method of the present invention is modified so that the method defined in the above-mentioned “ultraviolet absorptiometry” can be executed without using a pressure vessel when automation is assumed. Specifically, in step 1, an alkali metal salt of peroxodisulfuric acid is added to the test water, and the test water is heated from 90 ° C. to a temperature at which the test water boils (preferably 100 ° C.). It is preferable to heat in a temperature range of ≦ C.

  The alkali metal peroxodisulfate used here is usually potassium peroxodisulfate or sodium peroxodisulfate. In general, it is preferable to add the alkali metal peroxodisulfate to the inspection water as an aqueous solution. In addition, the inspection water to which alkali metal peroxodisulfate is added can be adjusted to be alkaline by separately adding an alkaline aqueous solution such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide or barium hydroxide. it can. The peroxodisulfuric acid alkali metal salt can be added to the inspection water as a solution of such an alkaline aqueous solution, and in this case, the inspection water can be adjusted to be alkaline without adding an alkaline aqueous solution separately.

  The amount of peroxodisulfate alkali metal salt is preferably set so that the total amount of the nitrogen compound contained in the test water can be sufficiently oxidatively decomposed, but if it is added excessively, unreacted alkali metal peroxodisulfate Salt may remain in the test water, which may cause false color development in step 2 described below. In particular, when the inspection water is heated in the temperature range from 90 ° C. to the temperature at which the inspection water boils in this step (preferably 100 ° C. or less), unreacted alkali metal peroxodisulfate tends to remain in the inspection water. For this reason, it is preferable that the concentration of the alkali metal peroxodisulfate in the test water adjusted to be alkaline is usually set to 0.5 to 20 g / L, and preferably set to 1 to 10 g / L. Is more preferable.

  The heating time in this process is such that the total amount of nitrogen compounds contained in the test water can be oxidatively decomposed and consumed completely or self-decomposed so that the alkali metal peroxodisulfate remains partially unreacted. Is preferably set so that it disappears, usually 30 to 120 minutes. In addition, when the heating time in this process becomes long to eliminate peroxodisulfuric acid alkali metal salt, after heating for a sufficient time for oxidative decomposition of the nitrogen compound contained in the test water, the test water is irradiated with ultraviolet rays, etc. The remaining alkali metal peroxodisulfate can be oxidatively decomposed by performing the above-mentioned treatment. In this case, the heating time in this step can be shortened.

  Next, vanadium (III) chloride and a diazotizing reagent are added to the test water that has undergone step 1 and reacted under acidic conditions (step 2). Here, vanadium (III) chloride acts as a reducing agent under acidity on nitrate ions contained in the test water, that is, nitrate ions originally contained in the test water and nitrate ions generated in step 1, and nitrate ions. Is converted to nitrite ion. The produced nitrite ion reacts with a diazotization reagent under acidity to produce a diazonium salt. Here, reduction of nitrate ions by vanadium (III) chloride is not inhibited even in the presence of a diazotizing reagent and can proceed stably. Moreover, the formation reaction of the diazonium salt by the diazotizing reagent is not inhibited even in the presence of vanadium (III) chloride and can proceed stably. In addition, it is known, for example, in the following Non-Patent Document 2 that nitrate ions can be reduced to nitrite ions under acidic conditions by vanadium (III) chloride.

Yasuhiro Go, Analytical Chemistry, 55, 4, 259-262, 2006

  The amount of vanadium (III) chloride added to the test water is usually set so that the total amount of nitrate ions contained in the test water can be reduced to nitrite ions. Usually, the required chemicals are added in this process. It is preferable that the concentration in the test water after the test is 0.1 to 2.0 g / L, and more preferably 0.2 to 1.0 g / L.

  The diazotizing reagent used in this step can generate a diazonium salt by reaction with nitrite ion, in particular, the test water can be colored by itself by adding to the test water, and at the same time, the formed diazonium Inspection water can be colored with salt. Such a diazotizing reagent is usually selected from the group consisting of a group of aromatic primary amine compounds having a ketone group or a nitro group and a group of 3-amino-2-cyclohexen-1-one skeleton-containing compounds. Compounds can be used.

  The group of aromatic primary amine compounds includes an aromatic primary amine compound having a ketone group or a nitro group at the ortho position or para position, and an aromatic group having a ketone group or a nitro group at the meta position. It consists of 2nd group which consists of a primary amine compound.

  The first group includes, for example, 1-aminoanthraquinone, 2-nitroaniline, sodium 4-nitroaniline-2-sulfonate, p-nitroaniline, 2-amino-3-hydroxyanthraquinone, 1-amino-4-bromoanthraquinone 2-sulfonic acid sodium, 2-amino-2′-fluoro-5-bromobenzophenone, 4-aminobenzophenone, 4-fluoro-2-nitroaniline, 5-amino-2-nitrobenzotrifluoride, 4-amino- Such as 3-nitrobenzophenone, 2-amino-5-nitrobenzophenone and 4,6-dinitro-o-toluidine, but 1-aminoanthraquinone, 2-nitroaniline, sodium 4-nitroaniline-2-sulfonate, p -Nitroaniline, 2-amino-3-hydroxyanthra Made of non-and 1-amino-4-sodium-bromo anthraquinone-2-sulfonic acid is particularly preferred.

  On the other hand, the second group includes, for example, 3′-aminoacetophenone, 3-aminobenzophenone, 2-amino-9-fluorenone, m-nitroaniline, 2-chloro-5-nitroaniline and the like. Those consisting of acetophenone and 3-aminobenzophenone are preferred.

  The group of 3-amino-2-cyclohexen-1-one skeleton-containing compounds includes, for example, 3-amino-2-cyclohexen-1-one, 2-amino-3-chloro-1,4-naphthoquinone and 3-amino- Including 5,5-dimethyl-2-cyclohexen-1-one, etc., those consisting of 3-amino-2-cyclohexen-1-one and 2-amino-3-chloro-1,4-naphthoquinone are particularly preferred.

  The diazotizing reagent is usually preferably added to the test water as a solution dissolved in a solvent. Examples of the solvent used for dissolving the diazotizing reagent include pure water obtained by membrane treatment with a reverse osmosis membrane or the like, purified water such as distilled water and ion-exchanged water, dimethyl sulfoxide, N, N-dimethyl Examples include formamide, acetone, and alcohols such as methanol, ethanol, propanol, butanol, polyethylene glycol, and glycerin.

The amount of diazotizing reagent added to the test water must be set to an amount sufficient for the total amount of nitrite ions contained in the test water to participate in the formation of the diazonium salt, and is assumed to be included in the test water. At least equimolar to the nitrite ion produced. In this regard, in consideration of nitrite ions derived from nitrogen compounds contained in test water via nitrate ions, the concentration of nitrite ions contained in test water is generally about 0 to 35 mg [NO ₂ ⁻ ] / L. Therefore, for example, when the amount of test water is 2.0 mL, the amount of diazotizing reagent added is usually preferably set to 1.5 μmol or more. However, when the nitrite ion concentration in the test water is found to be significantly lower than 35 mg [NO ₂ ⁻ ] / L, or as expected, the addition amount of the diazotization reagent is less than 1.5 μmol. It may be.

  In this step, the reduction reaction of nitrate ion by vanadium (III) chloride and the formation reaction of diazonium salt by the reaction of diazotization reagent and nitrite ion are advanced by heating under acidic conditions. Specifically, the test water is adjusted to acidic by adding to the test water an acid that does not contain nitrogen elements that may affect the quantitative results of total nitrogen and does not inhibit the reaction in this process. Let the reaction proceed below. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, organic acids such as acetic acid, benzenesulfonic acid, citric acid and succinic acid, and aqueous solutions thereof. Usually, hydrochloric acid aqueous solution (dilute hydrochloric acid) or sulfuric acid aqueous solution is used. (Diluted sulfuric acid) is preferably used.

  The amount of acid added to the test water is preferably set so that the test water can be adjusted to be acidic so that the reaction in this step proceeds smoothly and stably. Usually, the pH of the test water is 3 or less. It is preferable to set so that it is particularly preferably set to be 0 to 1.5.

  Here, the acid is preferably added to the test water as a solvent for vanadium (III) chloride. That is, the test water is preferably adjusted to be acidic by adding an acid solution of vanadium (III) chloride. In this case, it is particularly preferable to use dilute hydrochloric acid or dilute sulfuric acid as the acid. If the test water after the completion of step 1 is alkaline, adding vanadium (III) chloride there will result in precipitation as vanadium hydroxide, but when vanadium (III) chloride is added as an acid solution, Thus, the added vanadium (III) chloride can stably reduce nitrate ions.

  In addition, although vanadium (III) chloride can also be added to test water as the aqueous solution prepared using the above-mentioned purified water, in this case, the addition time of the acid with respect to test water is the aqueous solution of vanadium (III) chloride. It is preferable before adding. By doing in this way, precipitation of the above vanadium hydroxide can be suppressed. However, when the alkali metal peroxodisulfate used in Step 1 becomes an acidic compound by autolysis, it has an action of shifting the pH of the test water to the acidic side. Therefore, if the test water at the end of step 1 is controlled to be neutral to acidic by adjusting the usage amounts of the alkaline aqueous solution and the alkali metal peroxodisulfate in step 1, vanadium chloride is added to the test water. It is also possible to add the acid after adding the aqueous solution of (III).

  The addition timing of the diazotizing reagent may be before or after the addition of the acid solution or acid of vanadium (III) chloride to the test water, and is not particularly limited.

  The heating temperature for the reaction in this step is usually preferably set to 60 to 100 ° C. When the heating temperature is less than 60 ° C., nitrate ions contained in the inspection water may not be easily reduced to nitrite ions. The time required for the reaction varies depending on the heating temperature and can be shortened as the heating temperature is increased, but is usually about 5 to 120 minutes.

  In this step, nitrite ions generated by reduction of nitrate ions react with a diazotization reagent under acidity adjusted with an acid to generate a diazonium salt. As a result, the test water colored by the addition of the diazotizing reagent is discolored by the diazotizing reagent itself as the diazotizing reagent is consumed by the reaction with nitrite ions, and at the same time, the test water colored by the diazonium salt is colored. Present.

  Next, the light absorbency of the test water which passed through the process 2 is measured (process 3). The absorbance measured here is the colored absorbance imparted to the test water by the diazotizing reagent remaining in the test water (hereinafter sometimes referred to as “absorbance A”), or the reaction of the diazotizing reagent. This is the colored absorbance (hereinafter sometimes referred to as “absorbance B”) imparted to the test water by the diazonium salt produced by the above.

  Absorbance A relates to the color imparted to the test water by the diazotizing reagent itself, and this coloration decreases in color intensity as the diazotized reagent is consumed by reaction with nitrite ions in the test water. For this reason, the absorbance A has a correlation with the diazotizing reagent concentration and the nitrite ion concentration in the test water. The measurement wavelength of absorbance A is the maximum absorption wavelength of the color imparted to the test water by the diazotization reagent or a wavelength in the vicinity thereof, and is not specified because it varies depending on the type of diazotization reagent used. It is in the range of ~ 600 nm.

  On the other hand, the absorbance B relates to the color imparted to the test water by the diazonium salt produced by the reaction, and this color increases as the diazonium salt concentration increases as the reaction proceeds. And since a diazonium salt density | concentration increases according to the nitrite ion density | concentration of test water, the light absorbency B and the nitrite ion density | concentration in the test water which passed through the process 1 have a correlation. The measurement wavelength of absorbance B is the maximum absorption wavelength of the coloring that the diazonium salt produced imparts to the test water or a wavelength in the vicinity thereof, and is specified because it varies depending on the type of diazonium salt produced (that is, the type of diazotization reagent used) Although not, it is usually in the range of 250-600 nm.

In this step, the amount of nitrite ions in the test water is determined from the measured value of absorbance A or absorbance B based on a calibration curve prepared by examining the relationship between absorbance A or absorbance B and nitrite ion concentration in advance. To do. The calibration curve created here has a good linear relationship between the nitrite ion concentration and the absorbance A or absorbance B up to a relatively high concentration of nitrite ion concentration. The quantifiable range of nitrate ions is in the range of 0 to 53 mg [NO ₂ ⁻ ] / L, which is wider than the range possible with conventional methods such as the JIS method.

  The total nitrogen concentration of the inspection water can be obtained by converting from the quantitative result of nitrite ions obtained in step 3. The above-described quantifiable range of nitrite ions in step 3 corresponds to a wide range of 0 to 16 mg [N] / L in terms of total nitrogen. Therefore, the quantification method of the present invention is effective as a method for measuring the total nitrogen concentration of test water containing nitrogen compounds.

  In step 3, in order to increase the reliability of the quantitation result of nitrite ions, both absorbance A and absorbance B are measured, and the amount of nitrite ions in the test water is determined separately based on each absorbance. You can also. In this case, if the determination result based on the absorbance A substantially matches the determination result based on the absorbance B, it can be determined that the reliability of the quantitative result is high.

  When measuring the absorbance A in step 3, the quantification method of the present invention preferably includes a step (step 3 ′) of adjusting the pH of the test water passed through step 2 to be higher than 7 before step 3. . Absorbance A may cause some errors in the quantitation results of nitrite ions because the value may vary depending on the pH value when the pH of the test water is 7 or less. In addition, since the measurement error due to the influence of pH is reduced, the absorbance A can further improve the quantitative accuracy of the nitrite ion concentration.

  The pH of the inspection water can usually be adjusted by adding an alkali compound such as an alkali metal hydroxide, carbonate or hydrogen carbonate or an aqueous solution thereof to the inspection water after completion of step 2. Is preferably adjusted by adding an aqueous sodium hydroxide solution.

  In a preferred embodiment of the quantification method of the present invention (Form 1), a diazotization reagent is selected from the first group consisting of an aromatic primary amine compound having a ketone group or a nitro group in the ortho or para position in Step 2. In step 3, the absorbance A is measured. In this case, the diazotization reagent is easily consumed by the reaction with nitrite ions in the test water, and the coloring intensity due to the diazotization reagent tends to be lowered, so that the nitrite ion concentration quantitative accuracy can be easily increased.

However, the diazonium salt produced in Step 2 of this form is a compound in which the diazonium group (—N ₂ ⁺ ) of the diazonium ion forming it is easily decomposed and the group is converted to a hydroxyl group (—OH) ( Hereinafter, it may be referred to as a conversion compound). In particular, since Step 2 is performed under heating, the generation of such a conversion compound tends to proceed. For example, when 1-aminoanthraquinone is used as a diazotization reagent, the diazonium group of the diazonium ion is converted to a hydroxyl group, and 1-hydroxyanthraquinone is generated as a conversion compound. The hydroxyl group of the resulting conversion compound has a lone pair like the amino group (—NH ₂ ) of the diazotization reagent, and thus forms a conjugated system with the aromatic structure moiety to which it is bonded. For this reason, the conversion compound colors test water as another dye having a maximum absorption wavelength at a wavelength close to the maximum absorption wavelength of the diazotizing reagent, and may affect the absorbance measured in step 3. For example, in the absorption spectrum of coloring due to 1-aminoanthraquinone, the maximum absorption wavelength is around 480 nm, whereas in the absorption spectrum of coloring due to 1-hydroxyanthraquinone which is a conversion compound, the maximum absorption wavelength is around 400 nm. For this reason, when measuring the absorbance using a light source such as a light emitting diode in step 3, the light source emits light having a wavelength range, so that the conversion compound is used in the measurement of the target absorbance. Coloring of inspection water tends to be an obstacle.

  Therefore, in Step 2 of this embodiment, at least one compound selected from the group consisting of alcohol compounds and hypophosphorous acid and salts thereof together with vanadium chloride (III) and a diazotizing reagent in test water (hereinafter, It may be referred to as “additive”.) Is preferably added. When such an additive is added, the diazonium ion of the diazonium salt generated in step 2 is converted into a compound different from the conversion compound by the rapid reduction of the diazonium group to a hydrogen atom. For example, when the diazotizing reagent is 1-aminoanthraquinone, in this step, the production of 1-hydroxyanthraquinone is suppressed, and anthraquinone is produced instead. This other compound is difficult to color the test water because the hydrogen atom resulting from the reduction of the diazonio group is not involved in the conjugated system of the aromatic structure portion, and hardly affects the absorbance measurement in step 3.

  Examples of alcohol compounds that can be used as additives include ethanol, methanol, propanol, butanol, polyethylene glycol, and glycerin. Examples of hypophosphites include sodium hypophosphite, potassium hypophosphite and calcium hypophosphite, and hydrates of these hypophosphites.

  In general, the additive is preferably added to the inspection water as a solution dissolved in a solvent. Examples of the solvent include the aforementioned purified water and dimethyl sulfoxide. Moreover, an additive can also be added to test water as a solution of the acid used for setting test water acidic, or its aqueous solution. Furthermore, when the diazotizing reagent is added to the test water as a solution in alcohols, alcohols used as solvents can be used as additives.

  The amount of additive added to the test water is preferably set to an amount sufficient to reduce the total amount of diazonium ions of the diazonium salt produced by the reaction in step 2, and is usually diazotized to be added to the test water. It is preferable to set at least equimolar with the reagent amount.

  In still another preferred embodiment (Form 2) of the quantification method of the present invention, a diazotization reagent is selected from the second group consisting of an aromatic primary amine compound having a ketone group or a nitro group at the meta position in Step 2. In step 3, the absorbance A is measured. In still another preferred embodiment (Form 3) of the quantification method of the present invention, a diazotization reagent is selected from the group of 3-amino-2-cyclohexen-1-one skeleton-containing compounds in Step 2, and Step 3 Absorbance A is measured. Even in these cases, the diazotization reagent is easily consumed by the reaction with nitrite ions in the test water, and the coloring intensity due to the diazotization reagent tends to be lowered, so that it is easy to improve the quantification accuracy of the nitrite ion concentration.

  In Embodiments 1 to 3, it is particularly preferable to set the pH of the test water that has passed through step 2 to be higher than 7 before step 3 in order to suppress the measurement error of absorbance A due to the influence of pH. .

  In still another preferred embodiment of the quantification method of the present invention, a diazotizing reagent is selected from the second group consisting of an aromatic primary amine compound having a ketone group or a nitro group at the meta position in Step 2; Absorbance B is measured. In this case, the reaction between the diazotizing reagent of the second group and nitrite ions in the test water is likely to proceed, and the coloring intensity due to the generated diazonium salt is likely to increase, so that the quantitative accuracy of the nitrite ion concentration can be easily increased.

  As the various aqueous solutions used in the quantification method of the present invention, those prepared using the above-described purified water may be used other than those specified to be prepared using the above-described purified water. preferable.

Reagents and spectrophotometers The reagents and spectrophotometers used in the following examples and the like are as follows.
Nitrite nitrogen standard solution (for ion chromatograph): Wako Pure Chemical Industries, Ltd. Code 147-06341
10% by weight hydrochloric acid: Wako Pure Chemical Industries, Ltd. Code 085-07535
1 mol / L hydrochloric acid: Wako Pure Chemical Industries, Ltd. Code 083-01095
10 w / v% sodium hydroxide solution: Wako Pure Chemical Industries, Ltd. Code 191-1555
1 mol / L sodium hydroxide solution: Wako Pure Chemical Industries, Ltd. Code 192-02175
0.2 mol / L sodium hydroxide aqueous solution: The above 1 mol / L sodium hydroxide solution diluted 5 times with distilled water.
Vanadium (III) chloride: Sigma Aldrich Japan Co., Ltd. Code 208272
L-glutamic acid: Wako Pure Chemical Industries, Ltd. Code 074-00505
Ammonium sulfate: Wako Pure Chemical Industries, Ltd. Code 019-03435
Potassium peroxodisulfate: Wako Pure Chemical Industries, Ltd. Code 169-11891
Sodium hydroxide-potassium peroxodisulfate solution: prepared according to the description of Japanese Industrial Standards JIS K0102 “Factory Wastewater Test Method (2008)”, 45.2 “Ultraviolet Spectrophotometry”, a) Reagent, 4). The sodium hydroxide used here is for measuring nitrogen (code 191-08625) manufactured by Wako Pure Chemical Industries, Ltd., and potassium peroxodisulfate is as described above.
Sodium hypophosphite monohydrate: Wako Pure Chemical Industries, Ltd. Code 193-02225
1-propanol: Wako Pure Chemical Industries, Ltd. Code 162-04816
Dimethyl sulfoxide (reagent special grade): Wako Pure Chemical Industries, Ltd. Code 043-07216
1-aminoanthraquinone: Tokyo Chemical Industry Co., Ltd. Code A0590
2-Nitroaniline: Tokyo Chemical Industry Co., Ltd. Code N0118
p-Nitroaniline: Tokyo Chemical Industry Co., Ltd. Code N0119
Sodium 4-nitroaniline-2-sulfonate: Tokyo Chemical Industry Co., Ltd. Code A0375
2-Amino-3-hydroxyanthraquinone: Tokyo Chemical Industry Co., Ltd. Code A0315
3'-aminoacetophenone: Tokyo Chemical Industry Co., Ltd. Code A0249
3-Aminobenzophenone: Tokyo Chemical Industry Co., Ltd. Code A1899
3-Amino-2-cyclohexen-1-one: Tokyo Chemical Industry Co., Ltd. Code A1936
2-Amino-3-chloro-1,4-naphthoquinone: Tokyo Chemical Industry Co., Ltd. Code A1288
Sodium 1-amino-4-bromoanthraquinone-2-sulfonate: Tokyo Chemical Industry Co., Ltd. Code A0279
Sulfanilamide (special grade reagent): Wako Pure Chemical Industries, Ltd. Code 191-0502
Naphthylethylenediamine (for nitrogen oxide measurement): Wako Pure Chemical Industries, Ltd. Code 147-04141
Spectrophotometer: Shimadzu Corporation trade name “UV-1600PC”

Example 1
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 4.0, 8.0, and 12.0 mg [N] / L were prepared. Nitrite ion solution with a nitrite ion concentration of 0 mg [N] / L uses distilled water as it is, and other nitrite ion solutions dilute a nitrite nitrogen standard solution with distilled water. Adjusted.

(Create a calibration curve)
For 2.5 mL of each of the four types of prepared nitrite ion solutions, 1.0 mL of 1-propanol solution of 1-aminoanthraquinone (concentration 0.5 g / L), 10% by weight hydrochloric acid solution of vanadium (III) chloride (III) 1.0 mL of vanadium (III) chloride concentration 1.5 g / L) and 0.5 mL of distilled water were added, and the pH was set to 0.3. The nitrite ion solution was heated at 60 ° C. for 30 minutes, and then the absorption spectrum at 350 to 600 nm of the reaction solution was measured. The results are shown in FIG.

  Next, from the measured absorption spectrum, the absorbance at 480 nm (absorbance A), which is a coloring wavelength by 1-aminoanthraquinone, was extracted, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. The absorbance of each concentration of nitrite ion solution is shown in Table 1, and a calibration curve prepared based on Table 1 is shown in FIG. In Table 1, the amount of change in absorbance is the amount of change (amount of decrease) based on the absorbance of a nitrite ion solution having a nitrite ion concentration of 0.0 mg [N] / L. According to FIG. 2, the prepared calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

(Evaluation)
Japanese Industrial Standards JIS K0808 Standard for automatic determination of total nitrogen for water quality monitoring (2008) described in 6.2.4, containing L-glutamic acid and ammonium sulfate in the same amount in terms of nitrogen (mg [N] / L) By preparing a sample stock solution and diluting it, two types of test water samples having total nitrogen concentrations of 4.0 and 12.0 mg [N] / L were prepared.

  L-glutamic acid and ammonium sulfate contained in each test water sample were oxidatively decomposed by the method described in Japanese Industrial Standards JIS K 0102 “Factory Wastewater Test Method (2008)”, 45.2 “Ultraviolet Spectrophotometry”. More specifically, according to the method described in 1) to 4) of “c) Operation” of the same method, a sodium hydroxide-potassium peroxodisulfate solution was used, and L-glutamic acid and ammonium sulfate in each test water sample were 120. Oxidative decomposition was performed under heating conditions of 30 ° C. for 30 minutes.

  Next, with respect to 3.0 mL of each test water sample subjected to oxidative decomposition treatment, 1.0 mL of 1-propanol solution of 1-aminoanthraquinone and 10 weight of vanadium (III) chloride same as those used in preparing the calibration curve % Hydrochloric acid solution 1.0 mL was added and the pH was set to 0.3. And after heating each test water sample for 30 minutes at 60 degreeC, the light absorbency of 480 nm was measured about the reaction liquid, and the nitrite ion density | concentration of each test water sample was determined based on the analytical curve created from this light absorbency. The results are shown in Table 2.

Example 2
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, and 6.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
For each 2.0 mL of the four prepared nitrite ion solutions, 0.5 mL of dimethyl sulfoxide solution (concentration 0.3 g / L) of 2-nitroaniline, and 1 mol / L hydrochloric acid solution of vanadium (III) chloride (chloride) 0.2 mL of vanadium (III) concentration 10.0 g / L) and 0.4 mL of distilled water were added, and the pH was set to 1.2. After heating this nitrite ion solution at 95 ° C. for 20 minutes, an absorption spectrum of 315 to 515 nm of the reaction solution was measured. The results are shown in FIG.

  Next, from the measured absorption spectrum, the absorbance at 415 nm (absorbance A), which is the coloring wavelength by 2-nitroaniline, was extracted, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. The absorbance of each concentration of nitrite ion solution is shown in Table 3, and a calibration curve created based on Table 3 is shown in FIG. The amount of change in absorbance displayed in Table 3 is the same as in Table 1. According to FIG. 4, the prepared calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 6.0 mg [N] / L.

(Evaluation)
Two types of test water samples having a total nitrogen concentration of 2.0 and 6.0 mg [N] / L were prepared in the same manner as in Example 1.

  Each test water sample was subjected to oxidative decomposition treatment in the same manner as in Example 1. Then, for 2.4 mL of each test water sample after oxidative decomposition treatment, 0.5 mL of dimethyl sulfoxide solution of 2-nitroaniline and 1 mol / L hydrochloric acid solution of vanadium (III) chloride, which are the same as those used in the preparation of the calibration curve, are used. 0.2 mL was added and the pH was set to 1.2. And after heating each test water sample at 95 degreeC for 20 minute (s), the light absorbency of 415 nm was measured about the reaction liquid, and the nitrite ion density | concentration of each test water sample was determined based on the analytical curve created from this light absorbency. The results are shown in Table 4.

Example 3
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, and 6.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
For each 2.0 mL of the four types of prepared nitrite ion solutions, 0.4 mL of dimethyl sulfoxide solution (concentration 0.3 g / L) of p-nitroaniline, 1 mol / L hydrochloric acid solution (salt chloride) of vanadium (III) chloride 0.6 mL of vanadium (III) concentration 5.0 g / L) and 0.4 mL of distilled water were added, and the pH was set to 0.8. After heating this nitrite ion solution at 60 ° C. for 30 minutes, an absorption spectrum of 280 to 480 nm of the reaction solution was measured. The results are shown in FIG.

  Next, from the measured absorption spectrum, the absorbance at 380 nm (absorbance A), which is the color development wavelength by p-nitroaniline, was extracted, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. The absorbance of each concentration of nitrite ion solution is shown in Table 5, and a calibration curve prepared based on Table 5 is shown in FIG. The amount of change in absorbance displayed in Table 5 is the same as in Table 1. According to FIG. 6, the prepared calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 6.0 mg [N] / L.

(Evaluation)
Two types of test water samples having a total nitrogen concentration of 2.0 and 6.0 mg [N] / L were prepared in the same manner as in Example 1.

  Each test water sample was subjected to oxidative decomposition treatment in the same manner as in Example 1. And for 2.4 mL of each test water sample after oxidative decomposition treatment, 0.4 mL of dimethyl sulfoxide solution of p-nitroaniline and 1 mol / L hydrochloric acid solution of vanadium (III) chloride same as those used in preparing the calibration curve 0.6 mL was added and the pH was set to 0.8. And after heating each test water sample for 30 minutes at 60 degreeC, the light absorbency of 380 nm was measured about the reaction liquid, and the nitrite ion density | concentration of each test water sample was determined based on the analytical curve created from this light absorbency. The results are shown in Table 6.

Example 4
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 4.0, 8.0, and 12.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
For each 2.5 mL of the four types of prepared nitrite ion solutions, 1.0 mL of 1-aminoanthraquinone dimethyl sulfoxide solution (concentration 0.5 g / L), 10 wt% hydrochloric acid solution of vanadium (III) chloride (salt chloride) Vanadium (III) concentration 10.0 g / L) 0.15 mL, 10 wt% hydrochloric acid solution of sodium hypophosphite monohydrate (sodium hypophosphite monohydrate concentration including water molecules 5 g / L) 1.0 mL and 0.5 mL distilled water were added and the pH was set to 0.2. The nitrite ion solution having the pH set as described above was heated at 95 ° C. for 10 minutes, and then the absorption spectrum at 350 to 600 nm of the reaction solution was measured. The results are shown in FIG.

  Next, from the measured absorption spectrum, the absorbance at 480 nm (absorbance A), which is a coloring wavelength by 1-aminoanthraquinone, was extracted, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. The absorbance of each concentration of nitrite ion solution is shown in Table 7, and a calibration curve created based on Table 7 is shown in FIG. The amount of change in absorbance displayed in Table 7 is the same as in Table 1. According to FIG. 8, the prepared calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

(Evaluation)
Two types of test water samples having total nitrogen concentrations of 4.0 and 12.0 mg [N] / L were prepared in the same manner as in Example 1.

  Potassium peroxodisulfate was dissolved in a 0.2 mol / L sodium hydroxide aqueous solution to prepare a solution having a potassium peroxodisulfate concentration of 30 g / L. 0.5 mL of the prepared solution was added to 2.5 mL of each test water sample, and each test water sample was heated at 95 ° C. for 60 minutes. Subsequently, 1.0 mL of a dimethyl sulfoxide solution of 1-aminoanthraquinone, which was the same as that used in the preparation of the calibration curve, 0.15 mL of a 10 wt% hydrochloric acid solution of vanadium (III) chloride, and sodium hypophosphite monohydrate 1.0 mL of 10 wt% hydrochloric acid solution was added and the pH was set to 0.2. And after heating each test water sample at 95 degreeC for 10 minute (s), the light absorbency of 480 nm was measured about the reaction liquid, and the nitrite ion concentration of each test water sample was determined based on the analytical curve created from this light absorbency. The results are shown in Table 8.

Reference example 1
[Reference Example 1A]
(Preparation of nitrite ion solution)
Seven kinds of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0 mg [N] / L Prepared in a similar manner.

(Create a calibration curve)
Add 2.0 mL of 1-propanol solution of 1-aminoanthraquinone (concentration 0.2 g / L) to 2.0 mL of each of the seven types of prepared nitrite ion solutions, and further add 0.5 mL of 10 wt% hydrochloric acid. The pH was set to 0.6 by addition. After this nitrite ion solution was allowed to react at 25 ° C. for 15 minutes, an absorption spectrum of 282 to 600 nm of the reaction solution was measured. The results are shown in FIG.

  Next, the absorbance (absorbance A) at 480 nm, which is the color development wavelength by 1-aminoanthraquinone, was extracted from the measured absorbance spectrum, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. In addition, absorbance at 330 nm (absorbance B), which is a coloring wavelength of the diazonium salt generated by the reaction, was extracted from the measured absorption spectrum, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. These results are shown in FIG. According to FIG. 10, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

[Reference Example 1B]
After the nitrite ion solution adjusted to pH 0.6 was allowed to react at 25 ° C. for 15 minutes, 0.6 mL of 10 w / v% sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.4. Except that the absorption spectrum was measured after the adjustment, the same operation as in Reference Example 1A was performed to prepare two types of calibration curves. The measurement result of the absorption spectrum is shown in FIG. 11, and the calibration curve is shown in FIG. According to FIG. 12, each of the two types of prepared calibration curves shows high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

[Reference Example 1C]
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, and 6.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
Add 0.5 mL of 2-nitroaniline dimethyl sulfoxide solution (concentration 0.3 g / L) to 2.0 mL of each of the four types of prepared nitrite ion solutions, and then add 0.2 mL of 1 mol / L hydrochloric acid. The pH was set to 1.2. After this nitrite ion solution was allowed to react at 25 ° C. for 10 minutes, the absorption spectrum of 240 to 500 nm of the reaction solution was measured. The results are shown in FIG.

  Next, the absorbance (absorbance A) at 410 nm, which is the color development wavelength by 2-nitroaniline, was extracted from the measured absorbance spectrum, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. Further, the absorbance at 280 nm (absorbance B), which is the color development wavelength of the diazonium salt generated by the reaction, was extracted from the measured absorption spectrum, and a calibration curve for determining the nitrite ion concentration was created from this absorbance. These results are shown in FIG. According to FIG. 14, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 6.0 mg [N] / L.

[Reference Example 1D]
After allowing the nitrite ion solution adjusted to pH 1.2 to react at 25 ° C. for 10 minutes, 0.4 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.7. Then, the same operation as in Reference Example 1C was performed except that the absorption spectrum was measured, and two types of calibration curves were prepared. The measurement result of the absorption spectrum is shown in FIG. 15, and the calibration curve is shown in FIG. According to FIG. 16, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 6.0 mg [N] / L.

[Reference Example 1E]
(Preparation of nitrite ion solution)
Five types of nitrite ion solutions having nitrite ion concentrations of 0.0, 0.5, 1.0, 1.5, and 2.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
0.2 mL of an aqueous solution of sodium 4-nitroaniline-2-sulfonate (concentration 0.6 g / L) is added to 2.0 mL of each of the five types of prepared nitrite ion solutions, and further 1 mol / L hydrochloric acid 0 2 mL was added to set the pH to 1.1. After this nitrite ion solution was allowed to react at 25 ° C. for 10 minutes, the reaction solution was measured for absorbance at 370 nm (absorbance A), which is a coloration wavelength by sodium 4-nitroaniline-2-sulfonate. A calibration curve for determining the nitrite ion concentration from the absorbance was prepared. Moreover, about the reaction liquid, the light absorbency (absorbance B) of 260 nm which is a color development wavelength by the produced diazonium salt was measured, and the calibration curve for judging a nitrite ion concentration from this light absorbency was created. These results are shown in FIG. According to FIG. 17, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 2.0 mg [N] / L.

[Reference Example 1F]
After the nitrite ion solution adjusted to pH 1.1 was allowed to react at 25 ° C. for 10 minutes, 0.4 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.9. Reference was made, except that the absorbance at 370 nm (absorbance A), which was the color development wavelength by sodium 4-nitroaniline-2-sulfonate, and the absorbance at 260 nm (absorbance B), the color development wavelength by the formed diazonium salt were measured. In the same manner as in Example 1E, two types of calibration curves were created. The results are shown in FIG. According to FIG. 18, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 2.0 mg [N] / L.

[Reference Example 1G]
(Preparation of nitrite ion solution)
Six types of nitrite ion solutions having nitrite ion concentrations of 0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 mg [N] / L were prepared in the same manner as in Example 1. Prepared.

(Create a calibration curve)
Add 0.3 mL of dimethyl sulfoxide solution (concentration 0.33 g / L) of p-nitroaniline to 2.0 mL of each of the 6 prepared nitrite ion solutions, and then add 0.5 mL of 1 mol / L hydrochloric acid. The pH was set to 0.7. After allowing this nitrite ion solution to react at 25 ° C. for 5 minutes, the reaction solution was measured for absorbance at 380 nm (absorbance A), which is a color development wavelength by p-nitroaniline, and the concentration of nitrite ions was determined from this absorbance. A calibration curve for determining Moreover, about the reaction liquid, the light absorbency (absorbance B) of 310 nm which is the color development wavelength by the produced diazonium salt was measured, and the calibration curve for judging a nitrite ion concentration from this light absorbency was created. These results are shown in FIG. According to FIG. 19, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 5.0 mg [N] / L.

[Reference Example 1H]
After allowing the nitrite ion solution adjusted to pH 0.7 to react at 25 ° C. for 5 minutes, 0.7 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.8. Then, a calibration curve was prepared in the same manner as in Reference Example G, except that the absorbance at 380 nm (absorbance A), which was the color development wavelength by p-nitroaniline, was measured. The results are shown in FIG. According to FIG. 20, this calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 5.0 mg [N] / L.

[Reference Example 1I]
(Preparation of nitrite ion solution)
Five types of nitrite ion solutions having nitrite ion concentrations of 0.0, 4.0, 8.0, 12.0, and 16.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
1.5 mL of a dimethyl sulfoxide solution (concentration 0.5 g / L) of 2-amino-3-hydroxyanthraquinone is added to 2.5 mL of each of the five types of prepared nitrite ion solutions, and further 1 mol / L hydrochloric acid 0 .2 mL was added to set the pH to 1.3. This nitrite ion solution was allowed to react at 25 ° C. for 5 minutes, and then the absorbance at 520 nm (absorbance A), which is the coloring wavelength of 2-amino-3-hydroxyanthraquinone, was measured for this reaction solution. A calibration curve for determining the nitrite ion concentration was prepared. Moreover, about the reaction liquid, the light absorbency (absorbance B) of 460 nm which is the color development wavelength by the produced diazonium salt was measured, and the calibration curve for judging a nitrite ion density | concentration was created from this light absorbency. These results are shown in FIG. According to FIG. 21, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 16.0 mg [N] / L.

[Reference Example 1J]
After allowing the nitrite ion solution adjusted to pH 1.3 to stand at 25 ° C. for 5 minutes to react, 0.5 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.8. Then, the absorbance at 560 nm (absorbance A), which is the coloring wavelength by 2-amino-3-hydroxyanthraquinone, and the absorbance at 520 nm (absorbance B), which is the coloring wavelength by the formed diazonium salt, were measured, and then Reference Example 1I In the same manner, two types of calibration curves were created. The results are shown in FIG. According to FIG. 22, both of the two types of prepared calibration curves show high linearity at least in the range of nitrite ion concentration of 0 to 16.0 mg [N] / L.

[Reference Example 1K]
(Preparation of nitrite ion solution)
Five types of nitrite ion solutions having nitrite ion concentrations of 0.0, 0.5, 1.0, 1.5, and 2.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
0.1 mL of a dimethyl sulfoxide solution (concentration 0.33 g / L) of 3-amino-2-cyclohexen-1-one was added to 2.0 mL of each of the five types of prepared nitrite ion solutions, and further 1 mol / The pH was set to 1.1 by adding 0.2 mL of L hydrochloric acid. After this nitrite ion solution was allowed to react at 25 ° C. for 10 minutes, the reaction solution was measured for the absorbance at 280 nm (absorbance A), which is the coloring wavelength of 3-amino-2-cyclohexen-1-one, A calibration curve for determining the nitrite ion concentration from this absorbance was prepared. The results are shown in FIG. According to FIG. 23, this calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 2.0 mg [N] / L.

[Reference Example 1L]
After the nitrite ion solution adjusted to pH 1.1 was allowed to react at 25 ° C. for 10 minutes, 0.4 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.9. Thereafter, a calibration curve was prepared in the same manner as in Reference Example 1K except that the absorbance at 270 nm (absorbance A), which was the color development wavelength by 3-amino-2-cyclohexen-1-one, was measured. Moreover, about the reaction liquid, the light absorbency of 320 nm which is the color development wavelength by the produced | generated diazonium salt (absorbance B) was measured, and the analytical curve for judging a nitrite ion density | concentration from this absorbance was created. These results are shown in FIG. According to FIG. 24, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 2.0 mg [N] / L.

[Reference Example 1M]
(Preparation of nitrite ion solution)
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 4.0, 8.0, and 12.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
Add 1.0 mL of a dimethyl sulfoxide solution of 2-amino-3-chloro-1,4-naphthoquinone (concentration 0.5 g / L) to 2.0 mL of each of the four types of prepared nitrite ion solutions, and The pH was set at 1.3 by adding 0.2 mL of 1 mol / L hydrochloric acid. This nitrite ion solution was allowed to react at 95 ° C. for 30 minutes, and then an absorption spectrum at 300 to 600 nm was measured. The results are shown in FIG.

  Next, the absorbance at 460 nm (absorbance A), which is the color development wavelength of 2-amino-3-chloro-1,4-naphthoquinone, is extracted from the measured absorption spectrum, and a calibration for determining the nitrite ion concentration from this absorbance. Created a line. The results are shown in FIG. According to FIG. 26, this calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

[Reference Example 1N]
After allowing the nitrite ion solution adjusted to pH 1.3 to stand at 95 ° C. for 30 minutes to react, 0.5 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.9. A calibration curve was prepared in the same manner as in Reference Example 1M except that the absorption spectrum was measured. From the absorption spectrum, the calibration curve shows absorbance at 480 nm (absorbance A), which is a coloring wavelength by 2-amino-3-chloro-1,4-naphthoquinone, and absorbance at 330 nm (absorbance B), which is a coloring wavelength by the produced diazonium salt. Were extracted, and two types were prepared based on the respective absorbances. The measurement result of the absorption spectrum is shown in FIG. 27, and the calibration curve is shown in FIG. According to FIG. 28, both of the two types of prepared calibration curves show high linearity at least in the range of nitrite ion concentration of 0 to 12.0 mg [N] / L.

[Reference Example 1O]
(Preparation of nitrite ion solution)
Five types of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, 6.0, and 8.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
Add 1.0 mL of a 3'-aminoacetophenone dimethylsulfoxide solution (concentration 0.3 g / L) to 2.0 mL of each of the five prepared nitrite ion solutions, and add 0.2 mL of 1 mol / L hydrochloric acid. The pH was set to 1.2 by addition. This nitrite ion solution was allowed to react at 25 ° C. for 10 minutes, and then the absorbance of the reaction solution at 330 nm, which is the color development wavelength of the diazonium salt produced by the reaction of 3′-aminoacetophenone and nitrite ions. B) was measured, and a calibration curve for determining the nitrite ion concentration from this absorbance was prepared. The results are shown in FIG. According to FIG. 29, this calibration curve shows high linearity in the range of at least a nitrite ion concentration of 0 to 8.0 mg [N] / L.

[Reference Example 1P]
After allowing the nitrite ion solution adjusted to pH 1.2 to react at 25 ° C. for 10 minutes, 0.4 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.7. Thereafter, a calibration curve was prepared in the same manner as in Reference Example 1O except that the absorbance at 330 nm (absorbance A), which was the color development wavelength of 3′-aminoacetophenone itself, was measured. In addition, to measure the absorbance (absorbance B) at 310 nm, which is the coloring wavelength of the diazonium salt generated by the reaction of 3′-aminoacetophenone and nitrite ion, and determine the nitrite ion concentration from this absorbance. A calibration curve was created. These results are shown in FIG. According to FIG. 30, the two types of prepared calibration curves both show high linearity at least in the range of nitrite ion concentration of 0 to 8.0 mg [N] / L.

[Reference Example 1Q]
(Preparation of nitrite ion solution)
Five types of nitrite ion solutions having nitrite ion concentrations of 0.0, 2.0, 4.0, 6.0, and 8.0 mg [N] / L were prepared in the same manner as in Example 1.

(Create a calibration curve)
Add 1.0 mL of dimethyl sulfoxide solution of 3-aminobenzophenone (concentration 0.5 g / L) to 2.0 mL of each of the five prepared nitrite ion solutions, and then add 0.2 mL of 1 mol / L hydrochloric acid. The pH was set to 1.2. The nitrite ion solution was allowed to stand at 25 ° C. for 10 minutes, and then the absorbance (absorbance B) at 330 nm, which is the color developing wavelength of the diazonium salt produced by the reaction between 3-aminobenzophenone and nitrite ions, was measured. A calibration curve for determining the nitrite ion concentration was prepared. The results are shown in FIG. According to FIG. 31, this calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 8.0 mg [N] / L.

[Reference Example 1R]
After allowing the nitrite ion solution adjusted to pH 1.2 to react at 25 ° C. for 10 minutes, 0.4 mL of 1 mol / L sodium hydroxide solution was further added to the reaction solution to adjust the pH to 12.7. Thereafter, a calibration curve was prepared in the same manner as in Reference Example 1Q except that the absorbance (absorbance A) at 330 nm, which is the color development wavelength by 3-aminobenzophenone itself, was measured. The results are shown in FIG. According to FIG. 32, this calibration curve shows high linearity at least in the range of nitrite ion concentration of 0 to 8.0 mg [N] / L.

Comparative Example 1
Nitrite ion concentrations of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 mg [N ] 11 types of nitrite ion solutions were prepared in the same manner as in Example 1. And the naphthylethylenediamine absorptiometric method prescribed | regulated to Japanese Industrial Standard JISK0102, factory wastewater test method (2008) 43.1.1 (nonpatent literature 1) is applied with respect to each nitrite ion solution, and 540 nm The relationship between absorbance and nitrite ion concentration was investigated. The results are shown in FIG.

  According to FIG. 33, the quantifiable range of the nitrite ion concentration is limited to the range of 0 to 0.3 mg [N] / L, and it is understood that high concentration nitrite ions cannot be quantified by this method.

Reference example 2
[Reference Example 2A]
A nitrite ion solution having a nitrite ion concentration of 12.0 mg [N] / L was prepared in the same manner as in Example 1. The prepared nitrite ion solution is put into 2.5 mL of each of three test tubes A, B and C, and 1-aminoanthraquinone dimethyl sulfoxide solution (concentration 0.5 g / L) is added to the nitrite ion solution of each test tube. ) 1.0 mL was added. Moreover, 10% by weight hydrochloric acid was added in 0.5 mL portions, and the pH was set to 0.5. And after heating each test tube on the following conditions using a block heater, the absorption spectrum of 360-600 nm was measured. The results are shown in FIG. FIG. 34 also shows the result of measuring the same absorption spectrum (blank) immediately after the addition of the dimethyl sulfoxide solution of 1-aminoanthraquinone for test tube A and before heating.

Test tube A: 10 minutes at 95 ° C. Test tube B: 30 minutes at 95 ° C. Test tube C: 10 minutes at 85 ° C.

  According to FIG. 34, the absorption spectra of the test tubes A to C after the heating are inconsistent in the vicinity of 440 to 470 nm, which is close to 480 nm, which is the coloring wavelength by 1-aminoanthraquinone (within the one-dot chain line in FIG. 34). . This is because heating temperature and heating time are measured when the absorbance of 1-aminoanthraquinone coloring is measured using a light emitting diode having a broad emission wavelength centered around 480 nm or a phototransistor having a similar sensitivity wavelength. This means that the measurement result of the absorbance fluctuates due to the fluctuation of the nitrite, and the quantitative result of nitrite ion may be inaccurate.

[Reference Example 2B]
Except that the dimethyl sulfoxide solution of 1-aminoanthraquinone was changed to a 1-propanol solution of 1-aminoanthraquinone (concentration 0.5 g / L), the same operation as in Reference Example 2A was performed, and an absorption spectrum at 360 to 600 nm was measured. did. The results are shown in FIG. FIG. 35 also shows the result of measuring the same absorption spectrum (blank) immediately after addition of the 1-propanol solution of 1-aminoanthraquinone for test tube A and before heating.

  According to FIG. 35, the absorption spectra for the test tubes A to C after heating substantially coincide with each other even in the vicinity of 440 to 470 nm, which is close to 480 nm, which is a coloring wavelength by 1-aminoanthraquinone (inside the one-dot chain line in FIG. 35). ). Even if it is intended to measure the absorbance of coloring due to 1-aminoanthraquinone using a light-emitting diode having a broad emission wavelength centered around 480 nm or a phototransistor having a similar sensitivity wavelength, the heating temperature or This means that the absorbance measurement result does not substantially change due to fluctuations in the heating time, indicating that a highly reliable quantitative result of nitrite ions can be obtained.

[Reference Example 2C]
Four types of nitrite ion solutions having nitrite ion concentrations of 0.0, 4.0, 8.0, and 12.0 mg [N] / L were prepared in the same manner as in Example 1. The prepared four types of nitrite ion solutions (2.0 mL) were placed in individual test tubes, and each test tube was attached to a 90 ° C. block heater. Then, 0.8 mL of an aqueous solution (concentration 1.0 g / L) of sodium 1-amino-4-bromoanthraquinone-2-sulfonate and 0.5 mL of 10 wt% hydrochloric acid aqueous solution and 0.5 mL of distilled water were added to each test tube. And the pH was set to 0.5. After changing the heating temperature of the nitrite ion solution with a block heater to 95 ° C. and reacting for 15 minutes, the absorption spectrum of 360 to 600 nm of the reaction solution was measured. The results are shown in FIG.

  According to FIG. 36, the maximum absorption wavelength in the range of 420 to 540 nm varies due to the different concentrations of the nitrite ion solution. This is because, in the measured absorption spectrum, a colored absorption spectrum by sodium 1-amino-4-bromoanthraquinone-2-sulfonate and a sodium 1-amino-4-bromoanthraquinone-2-sulfonate via a diazonium salt This is probably because the absorption spectrum of the hydroxy form (sodium 1-hydroxy-4-bromoanthraquinone-2-sulfonate) produced in this manner appears in a fused state. In particular, the reason why the maximum absorption wavelength shifts to the lower wavelength side as the nitrite ion concentration is higher is considered to be because the production amount of the hydroxy compound is relatively increased due to the higher nitrite ion concentration.

[Reference Example 2D]
The point that 0.5 mL of sodium hypophosphite monohydrate aqueous solution in which the concentration of sodium hypophosphite monohydrate including water molecules was set to 10 g / L was added to the test tube instead of 0.5 mL of distilled water. The same operation as in Reference Example 2C was carried out except that, and an absorption spectrum of 360 to 600 nm of the reaction solution was measured. The results are shown in FIG.

  According to FIG. 37, even when the nitrite ion concentration is different, the maximum absorption wavelength in the range of 420 to 540 nm is substantially constant except when the sulfite ion concentration is 12.0 mg [N] / L. . This is because the use of an aqueous sodium hypophosphite monohydrate solution suppresses the formation of a hydroxy form as in Reference Example 2C, and the colored absorption spectrum of sodium 1-amino-4-bromoanthraquinone-2-sulfonate Is considered to be obtained stably.

Reference example 3
[Reference Example 3A]
Four diazotization reagent aqueous solutions prepared by adding 0.15 mL of a dimethyl sulfoxide solution (concentration 0.3 g / L) of p-nitroaniline as a diazotization reagent to 2.5 mL of distilled water were prepared. Three types of solutions with hydrogen ion concentrations adjusted to 0.011 mol / L, 0.022 mol / L and 0.033 mol / L by adding 0.03 mL, 0.06 mL and 0.09 mL of 1 mol / L hydrochloric acid to Prepared. After these solutions were allowed to stand at 25 ° C. for 5 minutes, an absorption spectrum at 290 to 480 nm was measured. The results are shown in FIG. In FIG. 38, the result of having measured the same absorption spectrum only about the diazotization reagent aqueous solution which has not added 1 mol / L hydrochloric acid is shown collectively.

[Reference Example 3B]
Four aqueous diazotization reagent solutions similar to those prepared in Reference Example 3A were prepared, and 0.03 mL, 0.06 mL, and 1 mol / L sodium hydroxide solution were used instead of 1 mol / L hydrochloric acid for each of the three. Three kinds of solutions whose pH was adjusted to 7 or more by adding 0.09 mL were prepared. These solutions were allowed to stand under the same conditions as in Reference Example 3A, and then the absorption spectrum was measured. The results are shown in FIG. In FIG. 39, the result of having measured the same absorption spectrum only about the diazotization reagent aqueous solution which has not added 1 mol / L sodium hydroxide solution is shown collectively.

[Reference Example 3C]
Three types of solutions with adjusted hydrogen ion concentrations were prepared in the same manner as in Reference Example 3A, and these solutions were allowed to stand at 25 ° C. for 5 minutes. Thereafter, 0.15 mL of a 1 mol / L sodium hydroxide solution was added to each solution to prepare three types of solutions with pH adjusted to 12.6, 12.5, and 12.3, respectively. The results of measuring the absorption spectrum of these solutions as in Reference Example 3A are shown in FIG. FIG. 40 shows the same absorption spectrum of a solution adjusted to pH 12.7 by adding only 0.15 mL of 1 mol / L sodium hydroxide solution to the same diazotizing reagent aqueous solution prepared in Reference Example 3A. The results of measuring are also shown.

[Description of Reference Examples 3A to 3C]
FIG. 38 relating to Reference Example 3A shows that the absorbance at the maximum absorption wavelength is different even when the concentration of p-nitroaniline, which is a diazotization reagent, is the same because the hydrogen ion concentration of the solution from which the absorption spectrum was measured is different. ing. More specifically, each time the hydrogen ion concentration of the solution increases by 0.011 mol / L, the absorbance at the maximum absorption wavelength decreases by about 5%. On the other hand, FIG. 39 relating to Reference Example 3B shows a maximum absorption wavelength in a solution having the same p-nitroaniline concentration when a 1 mol / L sodium hydroxide solution is added to the diazotizing reagent aqueous solution and the pH is set to 7 or more. It shows that there is no significant change in the absorbance. FIG. 40 relating to Reference Example 3C shows an absorption spectrum of a solution in which the hydrogen ion concentration was increased by adding 1 mol / L hydrochloric acid, and the pH was adjusted to 7 or more by adding 1 mol / L sodium hydroxide solution. Measurement shows that there is almost no change in absorbance at the maximum absorption wavelength.

  From the above results, when quantifying nitrite ions in the test water, it is considered preferable to measure the absorbance after adjusting the pH of the test water after the reaction of the diazotization reagent to 7 or more.

Claims (12)

A method for quantifying the total nitrogen of test water,
Adding an alkali metal salt of peroxodisulfuric acid to the test water and heating under alkalinity; and
Step 2 of adding vanadium (III) chloride and a diazotizing reagent capable of generating a diazonium salt by reaction with nitrite ion to the test water that has undergone Step 1 and heating under acidic conditions;
Step 3 of measuring the nitrite ion concentration by measuring at least one of the absorbance of coloring by the diazotizing reagent and the coloring absorbance of the generated diazonium salt with respect to the test water that has undergone Step 2. Including
As the diazotization reagent, a compound selected from the group consisting of an aromatic primary amine compound group having a ketone group or a nitro group and a 3-amino-2-cyclohexen-1-one skeleton-containing compound group is used.
Quantitative method for total nitrogen.   The method for quantifying total nitrogen according to claim 1, wherein in step 1, the inspection water is heated at a temperature from 90 ° C. to a boiling temperature.   The method further comprises a step of adjusting the pH of the test water having undergone the step 2 to be higher than 7 before the step 3, and measuring the absorbance of coloring by the diazotizing reagent in the step 3. The method for quantifying total nitrogen as described in 1.   The aromatic primary amine compound group includes an aromatic primary amine compound having a ketone group or a nitro group at the ortho position or para position, and an aromatic group having a ketone group or a nitro group at the meta position. The method for quantifying total nitrogen according to claim 1 or 2, comprising a second group consisting of primary amine compounds.   The first group is 1-aminoanthraquinone, 2-nitroaniline, sodium 4-nitroaniline-2-sulfonate, p-nitroaniline, 2-amino-3-hydroxyanthraquinone and 1-amino-4-bromoanthraquinone-2 The method for quantifying total nitrogen according to claim 4, comprising sodium sulfonate, wherein the second group comprises 3'-aminoacetophenone and 3-aminobenzophenone.   The 3-amino-2-cyclohexen-1-one skeleton-containing compound group comprises 3-amino-2-cyclohexen-1-one and 2-amino-3-chloro-1,4-naphthoquinone. The method for quantifying total nitrogen as described in 1.   The method for quantifying total nitrogen according to claim 4 or 5, wherein the diazotizing reagent is selected from the first group in step 2 and the absorbance of coloring by the diazotizing reagent is measured in step 3.   In step 2, together with vanadium chloride (III) and the diazotizing reagent, at least one compound selected from the group consisting of alcohol compounds and hypophosphorous acid and salts thereof is further added to the test water. The method for quantifying total nitrogen according to claim 7.   The method for quantifying total nitrogen according to claim 4 or 5, wherein the diazotizing reagent is selected from the second group in step 2 and the absorbance of coloring by the diazotizing reagent is measured in step 3.   The diazotization reagent is selected from the 3-amino-2-cyclohexen-1-one skeleton-containing compound group in step 2, and the absorbance of coloring by the diazotization reagent is measured in step 3. Method for the determination of total nitrogen.   The method for quantifying total nitrogen according to any one of claims 7 to 10, further comprising a step of adjusting the pH of the test water having undergone step 2 to be higher than 7 before step 3.   The method for quantifying total nitrogen according to claim 4 or 5, wherein the diazotizing reagent is selected from the second group in step 2 and the absorbance of coloring by the diazonium salt is measured in step 3.

Images