JPS581380B2 - Analysis method for nitrate nitrogen in water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for analyzing nitrate nitrogen in environmental water such as rivers, lakes, seawater, etc., or water such as wastewater.

In recent years, in connection with pollution prevention, the amount of nitrogen and nitrogen components in industrial wastewater and sanitary wastewater have attracted attention as a countermeasure against eutrophication of water bodies, and various studies are being conducted on methods of treating them.

In addition, from the perspective of water quality hygiene, the form of nitrogen compounds has been considered important as an indicator for determining the safety of drinking water from ancient times to today. It is hoped that it will be provided.

Methods for analyzing nitrate ions in water include the phenol disulfonic acid method and the sodium salicylate method, which are used in clean water testing methods to nitrate phenolic compounds.

Both methods are methods for quantifying by the concentration of a coloring substance produced by nitration of a phenol derivative.

Both methods are interfered with by chlorine ions and nitrite ions, and the operation is not necessarily easy, as the sample water needs to be evaporated to dryness on a water bath for nitration, but it is possible to test water as low as tap water with few interfering substances. Nitrate nitrogen of about 0.01 ppm can be determined.

Further, as a method for oxidizing organic compounds, there is a drinking water test method or a brucine method adopted in JISKO102 and the like.

In this method, in the presence of concentrated sulfuric acid, brucine is oxidized by nitrate ions and takes on a red color, which eventually turns yellow, and is determined by the concentration of the colored substance produced.

However, this method, like the phenol disulfonic acid method and the sodium salicylate method, is interfered with by chloride ions and nitrite ions.

If oxidizing and reducing substances are present, it is necessary to perform pretreatment with a reducing agent and an oxidizing agent.

Furthermore, pretreatment with aluminum hydroxide suspension and activated carbon is necessary to prevent turbidity and discoloration.

As described above, research on analytical methods for nitrate ions has been actively conducted in various places, but at present no good method has been found.

A method for reducing nitrate ions to nitrite ions is the cadmium/copper column method, which is used in clean water testing methods and marine observation guidelines.

However, this method requires extremely complicated operations such as column activation treatment and sample pretreatment, and requires a high level of skill, and also generates a large amount of hazardous waste liquid.

Further, the amount of nitrate nitrogen applied in this measurement method is about 2 to 20 μg, which is an extremely narrow range.

Another reduction method is to acidify the nitrate ion-containing sample water with an aqueous hydrochloric acid solution or the like to pH 2 to 4, then add zinc powder and reduce the sample water to nitrate and nitrite ions using nascent hydrogen.

However, this reduction method cannot be used as a quantitative method because the reduction rate is not constant.

The present invention has been made in view of this point, and a carrier gas bubble generating plate is provided in the reaction tube installed in the carrier gas flow path system of a nitrogen gas detector, and a sulfamic acid aqueous solution or a salt-containing sulfur A reaction solution consisting of an amino acid aqueous solution is held, and the ammonium ion concentration is 0.1 to 0.5 W/W% in sample water containing nitrate ions.
Add ammonium compound so that Using a gas that does not substantially contain nitrogen gas, this is passed through the air entrapment generating plate to generate fine bubbles of carrier gas, and the dynamic mixing contact caused by this causes the reaction to occur instantaneously. This method of analyzing nitrate nitrogen in water is characterized by expelling the reaction product gas from the reaction solution and introducing it into a nitrogen gas detector.

In the present invention, the mechanism for reducing nitrate ions to nitrite ions is based on active hydrogen generated by an ammine complex formation reaction of zinc by adding an ammonium compound and zinc powder to a nitrate ion-containing sample water and shaking the mixture.

As the ammonium compound used in this reduction method, ammonium compounds such as ammonium carbonate, ammonium acetate, ammonium chloride, ammonium sulfate, and ammonium citrate can be used.

The concentration of this ammonium compound added to the sample was 0.
It is preferable to add ammonium ion so that the ammonium ion concentration is 1 to 0.5 W/W%.

Zinc powder is added to the sample in an amount of 0.2 to IOW/W% and shaken.

The shaking and mixing time is preferably 20 seconds to 180 seconds.

As a method for detecting nitrogen gas, a thermal conduction detection method, a mass spectrometry method, or a discharge spectrum detection method can be used.

When using a gas chromatograph with a thermal conductivity type detector, helium, argon, or hydrogen gas can be used as the carrier gas, and the separation force ram can be filled with a packing material used for ordinary gas chromatographic analysis of inorganic gases, such as It is filled with silica gel, activated carbon, porous polymer beads, or molecular sieves, and the nitrogen gas generated from the reaction area is detected.

In the case of mass spectrometry, helium, argon, or hydrogen gas can be used as a carrier gas, and it is preferable to measure the nitrogen gas generated from the reaction part using mass fragmentography with m/e = 28 of a mass spectrometer. .

In the case of the discharge spectrum detection method, argon gas is used as a carrier gas, nitrogen gas generated from the reaction part is flowed into the detection cell, a high voltage is applied to the electrodes on both sides of the detection cell to cause a discharge, and the emission spectrum is detected using an optical filter. by 33
Only the wavelength of 71 Å can be extracted and electrically detected using a photomultiplier tube, making it possible to perform measurements with extremely high sensitivity.

As the reaction solution, a sulfamic acid water bath solution or a salt-containing sulfamic acid aqueous solution is used, and the sulfamic acid concentration is preferably 0.1 to 15% W/W.

As the salts, halides or sulfates of alkali metals such as sodium and potassium can be used.

A suitable salt concentration is 0.1 to 30 W/W%.

Good results can be obtained even if the reaction solution does not contain salts such as sodium chloride, but by adding salts such as sodium chloride, the carrier gas bubbles passing through the glass filter in the reaction tube become extremely small bubbles, and the generated nitrogen The gas becomes difficult to dissolve in the reaction solution or sample solution and is instantly expelled, which has the effect of improving the reproducibility of measurements.

Next, the method of the present invention will be explained in more detail with reference to the drawings, using a gas chromatograph equipped with a thermal conductivity type detector.

Figure 1 is an example of a schematic diagram of the apparatus used in the method of the present invention.
can use a gas such as helium or argon in a carrier gas cylinder.

The carrier gas is divided into two parts: one passes through the pressure regulator 4 and enters the reference side of the gas chromatograph, and the other passes through the pressure regulator 3 and the switching cock 7 and enters the reaction tube 9.

The flow rate of the carrier gas is suitably 20 to 100 ml/min.

The reaction tube is preferably made of hard glass and has an inner diameter of 8 to 15 mm above the glass filter 10 and an internal volume of 5 to 20 cm.

At the top of the glass filter, a capillary tube 12 and a cap 13 are provided for drawing out the reaction solution, sample solution, reaction-completed solution, or washing solution.

The glass filter is 2G or 3, which does not allow the reaction solution to pass through.
G, a thickness of 2 to 5 mm is suitable.

In addition, there is a sample liquid or reaction liquid inlet 1 at the top of the reaction tube.
4 is provided.

The sample solution or reaction solution may be introduced using a microsyringe or the automatic injection device 15.

The gas generated in the reaction solution or sample solution 11 is expelled from the solution and passes through the reaction solution droplet removal tube 17 to the oxidation-reduction tube 1.
introduced in 9.

The reaction liquid droplet removal tube is filled with gauze or the like impregnated with an indicator, so that if the reaction liquid droplets are entrained with the carrier gas, the tube will change color.

If volatile organic substances are present in the sample water, they will vaporize from the reaction tube, so they will be oxidized to carbon dioxide by the redox tube and removed by the deoxidizing gas tube 25.

The redox tube is filled with an oxidizing agent such as copper oxide or cobalt oxide and a reducing agent such as reduced copper or nickel, and has an inner diameter of 8 to 15 mm and a length of 15 to 30 cm.
using a quartz tube of 300 to 70
Heating to 0°C is suitable.

The gas discharged from the redox tube is introduced into a gas chromatograph equipped with a thermal conductivity detector 30 through a dehumidifying tube 22, a switching cock, and a deoxidizing gas tube.

The dehumidifying tube removes vaporized water from the reaction solution or sample solution, and is a glass tube filled with a dehydrating agent such as magnesium perchlorate, ion exchange resin for drying, calcium chloride, or silica gel.

The deacidifying gas pipe is a glass pipe filled with soda asbestos, soda lime, etc.

The gas chromatograph may have either a double column flow path or a single force ram flow path.

The separation force rams 28 and 29 can use packing materials commonly used in inorganic gas gas chromatographs, such as silica gel, activated carbon, porous polymer beads, or molecular sieves.

The signal obtained from the thermal conductivity type detector is recorded by a recorder 32 through a signal line 31.

On the other hand, the carrier gas branched from the conduit 2 is introduced into the dissolved air removal tube 37 through the 21 dollar valve 34 and the capillary tube 35.

Usually, about 15 pptn of nitrogen gas is dissolved in water, so dissolved air can be removed by putting the sample solution or reaction solution into a dissolved air removal tube and bubbling with a carrier gas.

Further, in order to prevent dissolution of air, a septum 36 having a pore for collecting a sample solution or a reaction solution is provided at the top of the dissolved air removal tube.

Each of the above parts is the conduit 2, 5, 6, 8, 16, 18, 21,
23, 24, 26, 27, and 33.

The present invention will be described below based on Examples, but the present invention is not limited thereto.

Example l The following measurements were carried out using the apparatus shown in FIG.

13mm inner diameter with 2m thick 2G glass filter
, using a hard glass reaction tube with an internal volume of 12 cm2, 3W
/W% Sodium chloride containing sulfamic acid 10W/W%
The aqueous reaction solution 3d was filled into a reaction tube and used.

20 to 40 for a dehumidifying pipe with an inner diameter of 9 mm and a length of 150 mm.
A oxidation-reduction tube with an inner diameter of 10 m and a length of 200 mm was filled with a mixture of equal amounts of mesh magnesium perchlorate and 20 to 40 mesh drying sulfonic acid type ion exchange resin, and a wire with a diameter of 0.6 mm and a length of 2 to 4 mm was filled. Copper oxide in the form of 8
0 mm, Q, 5 mm φ, 80 mm of linear reduced copper with a length of 2 to 4 mm, filled with copper oxide and reduced copper in that order, filled with 20 mm of quartz wool at both ends of the oxidation-reduction tube, and heated in an electric furnace for 500 mm.
It was heated to ℃ before use.

A glass reaction liquid droplet removal tube with an inner diameter of 9 mm and a length of 70 mm was filled with gauze impregnated with Fungo Red, and a deacidifying gas tube with an inner diameter of 9 mm and a length of 70 mm was filled with 20 to 40 gauze.
Filled with mesh soda asbestos.

A gas chromatograph separation column with an inner diameter of 3 mm and a length of 1
A 60-80 mesh stainless steel column was used and packed with 60 to 80 mesh activated carbon.

Using helium as a carrier gas and flowing at 60 ml/min,
It was used under the following conditions: column temperature 60°C, thermal conductivity detector temperature 60°C, and bridge current 160mA.

Nitrate nitrogen 20ppm using special grade reagent sodium nitrate
, lOppm and 5ppm aqueous solutions were prepared and 50m
Collect 25 ml in a stoppered test tube and add an ammonium compound aqueous solution (30 W/W% 0.65 for ammonium carbonate,
l, 26W/W% 1.0ml for ammonium chloride
, in the case of ammonium acetate, 50W/W% 0.6ml,
In case of ammonium sulfate, 30W/W% 1. Oml,
For ammonium citrate, 30W/W% 2.0m
After adding 1), 0.2 to 0.3 g of zinc powder was added, the container was tightly capped, and the mixture was shaken for 1 minute.

Immediately, No. Use 5C filter paper, length 7cm, inner diameter 1
After filtering approximately 6 ml into a 5 mm dissolved air removal tube and removing dissolved air with helium gas,
A calibration curve was created by introducing 0 μl.

A chromatogram was obtained in about 2 minutes, and when the relationship between nitrogen peak height and nitrate nitrogen concentration was plotted for each ammonium compound added, a good straight line was obtained as shown in FIG.

Using sodium nitrate as a standard, nitrate ions in various known component samples are reduced to nitrite ions with ammonium carbonate and zinc powder to prepare a 10 W/W% aqueous solution of sulfamic acid or 3 to 10 W/W of sulfamic acid containing various salts.
% aqueous solution, and the nitrate nitrogen concentration was measured by the peak height calibration curve method. Table 1 shows the results.

Example 2 Using the apparatus shown in FIG. 1, 25 ml of a sample solution containing trace amounts of nitrate ions was collected into a stoppered test tube, and a 1. Oml and zinc powder 0.
Add 25g and shake for 1 minute, then filter with A5C filter paper for about 1 minute.
Immediately introduce 3 ml of this filtrate into the reaction tube with a 5 ml syringe, leave it for about 4 minutes to drive out the dissolved air, and then remove the dissolved air with helium gas.
100 μl of a reaction solution of a 10 W/W % aqueous solution of sulfamic acid containing sodium chloride was introduced using a microsyringe, and a chromatogram of the generated nitrogen gas was recorded.

Note that the other measurement conditions were the same as in Example 1.

After the reaction, the sample is taken out of the system by opening and closing the cock, and 4 ml of distilled water or ion-exchanged water is introduced to clean the inside of the reaction tube, and after being pulled out to the outside by opening and closing the cock, the next sample solution is introduced one after another. Measurements were made.

A chromatogram was obtained in about 2 minutes after the introduction of the reaction solution, and when the relationship between the nitrogen peak height and the nitrate nitrogen concentration was plotted, a good straight line as shown in FIG. 3 was obtained.

Table 2 shows the results of measuring the nitrate nitrogen concentration in various known component samples using the peak height calibration curve method using sodium nitrate as a standard.

As described above, according to the analysis method of the present invention, rivers,
Nitrate nitrogen in environmental water such as lakes and seawater, tap water, industrial wastewater, sanitary wastewater, etc. can be easily, quickly, and accurately measured.

Note that nitrate ions and nitrite ions often coexist in sample water, and in this case, the content of nitrate nitrogen and nitrite nitrogen is directly quantified in the analysis method of the present invention.

However, if the sample water is directly reacted with the reaction solution of sulfamic acid aqueous solution without being reduced, only nitrite nitrogen is quantified, so the nitrate nitrogen concentration can be determined from the difference between the two.

[Brief explanation of the drawing]

FIG. j is a schematic diagram of an example of an apparatus for carrying out the method of the invention. In the figure, a carrier gas cylinder 1, pressure regulators 3 and 4, a switching cock between the reaction section and the detection section 7, a reaction tube 9, a glass filter 10, a reaction liquid or sample liquid 11, a capillary tube 12, a cock 13, a sample liquid or reaction Liquid injection port 14, automatic injection device 1
5. Reaction liquid droplet removal tube 17, redox tube 19, electric furnace 2
0, dehumidification pipe 22, deoxidizing gas pipe 25, separation column 28,
29, thermal conductivity type detector 30, signal line 31, recorder 32
, needle valve 34, capillary tube 35, septum 36 for dissolved air removal tube, dissolved air removal tube 37, conduits 2, 5, 6,
8, 16, 18, 21, 23, 24, 26, 27, 33
Each is shown separately. Figure 2 shows a calibration curve obtained by filling a reaction tube with a reaction solution and introducing 100 μl of a sample solution obtained by reducing a known sample of nitrate nitrogen with zinc powder in the coexistence of various ammonium compounds after removing dissolved air. ing. Figure 3 shows the calibration curve obtained by filling a reaction tube with 3 ml of a sample solution of a known trace amount of nitrate nitrogen reduced with zinc powder in the presence of ammonium chloride, and introducing 100 μg of the reaction solution after removing intoxicating air. It shows.

Claims (1)

[Claims] 1 In this method, the nitrate ions in the sample water containing nitrate ions are reduced to nitrite ions, the reduced solution is reacted in the carrier gas flow path system of the nitrogen gas detector, and the nitrogen gas is quantified with the nitrogen gas detector. A carrier gas bubble generating plate is installed in the reaction tube installed in the flow path system of the gas detector.
A reaction solution consisting of a sulfamic acid aqueous solution or a salt-containing sulfamic acid aqueous solution is held thereon, and an ammonium compound is added to the sample water containing nitrate ions so that the ammonium ion concentration becomes 0.1 to 0.5 W/W%. Then, add zinc powder in a neutral or weakly alkaline environment, shake it, and introduce a reducing solution in which nitrate ions are reduced to nitrite ions using active hydrogen generated by the ammine complex formation reaction, and substantially nitrogen gas is added as a carrier gas. Using a non-containing gas, the gas is passed through the bubble generating plate to generate fine carrier gas bubbles, which causes the reaction to occur instantaneously through dynamic mixing contact, and instantly removes the reaction product gas from the reaction liquid. A method for analyzing nitrate nitrogen in water, which is characterized by expelling it and introducing it into a nitrogen gas detector.