JP2017003528A - Ion chromatography analysis method of nitrite nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion chromatography analysis method of a nitrite nitrogen in which a dilute nitrite nitrogen (NO-N) can sufficiently be separated from a chloride ion (Cl) in an electrical conductivity detector.SOLUTION: An ion chromatography analysis method of a nitrite nitrogen is characterized by introducing a sample into a mobile phase while dipping the mobile phase into a column, separating ion species containing the nitrite nitrogen (NO-N) contained in the sample in the column, and detecting the separated ion species by an electrical conductivity detector. The filler is an anion exchanger having a quaternary ammonium group, the mobile phase is a water solution containing a sodium hydrogen carbonate and a sodium carbonate, and the content of the sodium hydrogen carbonate in the water solution is 2.0 times to 7.5 times of the sodium carbonate in the water solution in a mol ratio.SELECTED DRAWING: None

Description

  The present invention relates to an ion chromatography analysis method for nitrite nitrogen.

In ion chromatography, a sample containing ionic species is introduced into the eluent while passing the eluent through a column packed with a packing material for ion chromatography, and each ion species is retained in the column (elution time). This is an analysis method in which separation is performed using a difference in time), and the separated ions are detected and quantified using an electrical conductivity detector, an ultraviolet absorbance detector, or the like.
Nitrate-nitrogen (Nitrite nitrogen) is included in the water quality standard items stipulated in the ministerial ordinance (Ministry of Health, Labor and Welfare Ordinance No. 15 on February 28, 2014) that amends part of the ministerial ordinance on water quality standards, etc., which came into effect on April 1, 2014 NO ₂ -N) was added. The reference value relating to nitrite nitrogen (NO ₂ —N) in the water quality standard item is 0.04 mg / L or less. As an analysis of nitrite nitrogen (NO ₂ —N), for example, there is a method of analyzing all anions at the same time in a sample water added with ethylenediamine by ion chromatography. In the analysis by ion chromatography, the quantitative accuracy of nitrite nitrogen (NO ₂ —N) is required to clear 1/10 of the reference value, that is, 0.004 mg / L.

  Conventionally, as an analytical method by ion chromatography, for example, elution is performed using a column packed with a styrene-divinylbenzene copolymer having a quaternary ammonium group or an anion exchanger based on polyvinyl alcohol. A method using a sodium hydrogen carbonate aqueous solution and a sodium carbonate aqueous solution as the liquid is widely known (see, for example, Patent Document 1).

JP-A-8-2013365

However, in the above method, when 0.004 mg / L to 0.4 mg / L of nitrite nitrogen (NO ₂ —N) is measured, the conductivity detector detects chloride ions (Cl ^-) for receiving the interference by Determination of low concentrations of nitrite nitrogen (NO 2 _-N) is difficult, there is a problem that sometimes becomes undetectable nitrite nitrogen (NO 2 _-N).
Further, if an ultraviolet absorbance detector is used, nitrite nitrogen (NO ₂ -N) can be quantified without being disturbed by chloride ions (Cl ⁻ ), but the ultraviolet absorbance detector However, there is a problem in that, for example, chlorate ions, sulfate ions (SO ₄ ²⁻ ) and the like cannot be analyzed simultaneously because there are limitations on the ion species that can be detected.

The present invention has been made in view of such a situation, and in an electrical conductivity detector, a low concentration of nitrite nitrogen (NO ₂ —N) can be sufficiently separated from chloride ions (Cl ⁻ ). An object of the present invention is to provide an ion chromatography analysis method for nitrite nitrogen.

Accordingly, as a result of intensive studies to solve the above problems, the present inventors have used an anion exchanger having a quaternary ammonium group as a column packing, and sodium bicarbonate and By using an aqueous solution containing sodium carbonate, the sodium bicarbonate content in the aqueous solution is 2.0 to 7.5 times that of sodium carbonate in terms of molar ratio. It has been found that low concentrations of nitrite nitrogen (NO ₂ -N) can be detected without being disturbed by (Cl ⁻ ), and the present invention has been completed.

[1] A sample is introduced into a mobile phase while passing the mobile phase through a column packed with a packing material, and nitrite nitrogen (NO ₂ -N) contained in the sample is introduced into the column. Is a nitrite nitrogen ion chromatographic analysis method in which an ion conductivity analysis is performed, wherein the filler has a quaternary ammonium group. An anion exchanger, wherein the mobile phase is an aqueous solution containing sodium bicarbonate and sodium carbonate, and the content of the sodium bicarbonate in the aqueous solution is 2.0 by mole of the sodium carbonate in the aqueous solution. A method for ion chromatography analysis of nitrite nitrogen, characterized in that it is a factor of 7.5 to 7.5.

[2] The ion chromatography analysis method of nitrite nitrogen according to [1], wherein the polymer substrate constituting the anion exchanger having a quaternary ammonium group is polyvinyl alcohol.

[3] The ion chromatography analysis method of nitrite nitrogen according to [1] or [2], wherein the lower limit of quantification of the nitrite nitrogen (NO ₂ —N) is 0.004 mg / L or less.

According to the ion chromatography analysis method of nitrite nitrogen of the present invention, low concentration nitrite nitrogen (NO ₂ —N) is sufficiently separated from chloride ion (Cl ⁻ ) in an electric conductivity detector. Te, nitrite nitrogen _(NO 2 -N) can be quantified. That is, the ion chromatography analysis method of nitrite nitrogen of the present invention is 0.04 mg / min according to a ministerial ordinance (Ministry of Health, Labor and Welfare No. 15 on February 28, 2014) that revises a part of the ministerial ordinance on water quality standards. It is suitable as an analysis method for tap water in which the obligation to measure very low concentration of nitrite nitrogen (NO ₂ -N) of L or less is defined, and a quantitative accuracy of 0.004 mg / L or less can be realized.

It is a schematic diagram which shows an example of the ion chromatograph used by the ion chromatography analysis method of nitrite nitrogen of this invention. In Example 1, nitrite ion (NO ₂ ^-) which is the enlarged chromatogram near nitrite ion 0.003 mg / L added with the blank sample. In Example 1, a mixed sample containing 100 mg / L of chloride ion (Cl ⁻ ), 0.003 mg / L of nitrite ion (NO ₂ ⁻ ), and 5 mg / L of sulfate ion (SO ₄ ²⁻ ) was added. It is an enlarged chromatogram near nitrate ions. In Comparative Example 1, nitrite ion (NO ₂ ^-) which is the enlarged chromatogram near nitrite ion 0.003 mg / L added with the blank sample. In Comparative Example 1, a mixed sample containing 100 mg / L of chloride ion (Cl ⁻ ), 0.003 mg / L of nitrite ion (NO ₂ ⁻ ), and 5 mg / L of sulfate ion (SO ₄ ²⁻ ) was added. It is an enlarged chromatogram near nitrate ions.

An embodiment of an ion chromatography analysis method of nitrite nitrogen of the present invention will be described.
Note that this embodiment is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[Ion chromatography analysis of nitrite nitrogen]
The ion chromatography analysis method of nitrite nitrogen of the present invention is a method in which a sample is introduced into a mobile phase while passing the mobile phase through a column packed with a packing material. An ion chromatographic analysis method of nitrite nitrogen in which an ionic species containing nitrate nitrogen (NO ₂ -N) is separated and the separated ionic species is detected by an electrical conductivity detector, , An anion exchanger having a quaternary ammonium group, and the eluent is an aqueous solution containing sodium bicarbonate and sodium carbonate. The content of sodium bicarbonate in the aqueous solution is a molar ratio of sodium carbonate in the aqueous solution. This is a method of 2.0 times to 7.5 times. Accordingly, in the electrical conductivity detector, a low concentration of nitrite nitrogen (NO 2 _-N), chloride ions - can be measured without interference ^(Cl).

Note that the nitrite nitrogen _(NO 2 -N), a one of the nitrogen present in the form of nitric oxide, represented by _NO 2 -N, in water nitrite ^- present as (NO ₂₎ doing. In the ion chromatography analysis method of nitrite nitrogen of the present invention, nitrite nitrogen (NO ₂ —N) is quantified as nitrite ion (NO ₂ ⁻ ).

  An anion exchanger having a quaternary ammonium group has a base material and a quaternary ammonium group (anion exchange group) introduced to the base material directly or via a spacer.

As the substrate, for example, a styrene-divinylbenzene copolymer or a hydrophilic polymer can be used.
Examples of the hydrophilic polymer include polyvinyl alcohol and polyhydroxymethacrylate.

  Examples of the quaternary ammonium group include a trimethylammonium group, a triethylammonium group, an N, N-dimethylallylammonium group, and an N, N-dimethylbenzylammonium group.

The spacer is a chemical bonding site used for adjusting the distance between the base material and the quaternary ammonium group. The spacer is used to suppress interference between ions and the base material on the anion exchanger having a quaternary ammonium group. In the case where the substrate is a polymer having hydrophilicity, the spacer is preferably a divalent organic residue having ether bonds at both ends.
Examples of such a spacer include epichlorohydrin, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, and the like.

The content of the quaternary ammonium group in the anion exchanger having a quaternary ammonium group is preferably 0.01 meq to 0.1 meq per 1 g of the polymer forming the substrate, and 0.01 meq to 0 0.07 meq is more preferable, and 0.01 meq to 0.05 meq is even more preferable.
When the content of the quaternary ammonium group is 0.01 meq or more, the ion exchange action of the anion exchanger having a quaternary ammonium group does not decrease. In addition, if the content of the quaternary ammonium group is 0.1 meq or less, the anion exchanger having a quaternary ammonium group does not have an excessively strong ion exchange effect. NO ₂ -N) can be prevented from being adsorbed.

The size and shape of the anion exchanger having a quaternary ammonium group are not particularly limited. However, the low concentration of nitrite nitrogen _(NO 2 -N) chloride ion (Cl ^-) ability to sufficiently separate from, and detect low concentrations of nitrite nitrogen _(NO 2 -N) with high sensitivity For this purpose, the shape of the anion exchanger having a quaternary ammonium group is preferably a sphere having a volume average particle diameter of 1 μm to 30 μm, and a sphere having a volume average particle diameter of 3 μm to 10 μm. More preferred.
The volume average particle diameter of the anion exchanger having a quaternary ammonium group is measured with a Coulter counter.

  The anion exchanger having a quaternary ammonium group preferably has a strength that can withstand a pressure of 1 MPa to 30 MPa. Specifically, when an anion exchanger is packed in an ion chromatography column at 1 to 30 MPa, the peak shape of each ion is not affected, and when it is used for repeated measurement, the elution time and peak shape are changed over time. It is preferable not to change.

  Such an anion exchanger having a quaternary ammonium group can be produced, for example, according to the method described in JP-A-2006-242944.

The column is packed with the anion exchanger having the quaternary ammonium group. That is, the column is roughly composed of, for example, a cylindrical housing and the anion exchanger having the quaternary ammonium group filled in the housing.
The material and size of the housing are not particularly limited.
However, sufficiently separated low concentrations of nitrite nitrogen (NO 2 _-N), and, in order to detect low concentrations of nitrite nitrogen (NO 2 _-N) to a high sensitivity, for example, housing In the case of a cylindrical shape, the inner diameter of the housing is preferably 1.0 mm to 4.6 mm, and the length of the housing is preferably 100 mm to 250 mm. Further, when the housing is made of metal, the organic acid is adsorbed on the housing. Therefore, in order to sufficiently suppress the adsorption of the organic acid, the material of the housing is preferably a polyether ether ketone resin (PEEK).

The mobile phase is an aqueous solution containing sodium bicarbonate and sodium carbonate.
In this aqueous solution, the degree to which each ion elutes can be changed by adjusting the ratio of sodium bicarbonate and sodium carbonate.

In order to sufficiently separate low-concentration nitrite nitrogen (NO ₂ —N) from chloride ions (Cl ⁻ ), the content of sodium hydrogen carbonate in the above aqueous solution is in a molar ratio in the above aqueous solution. It is 2.0 times-7.5 times of sodium carbonate, and it is preferable that they are 2.0 times-4.0 times.
When the content of sodium hydrogen carbonate in the aqueous solution is less than 2.0 times the molar ratio of sodium carbonate in the aqueous solution, low concentration of nitrite nitrogen (NO ₂ -N) is reduced to chloride ions (Cl ⁻ ) Cannot be sufficiently separated from nitrite nitrogen (NO ₂ —N), and it becomes difficult to determine nitrite nitrogen (NO ₂ —N). On the other hand, when the content of sodium hydrogen carbonate in the aqueous solution exceeds 7.5 times that of sodium carbonate in the aqueous solution in a molar ratio, the elution time of nitrite nitrogen (NO ₂ -N) becomes longer, As the peak height decreases, it becomes difficult to distinguish from the baseline, and other coexisting ion species in the sample remain in the column without being eluted within the analysis time of one sample. May affect the measurement of other samples. Therefore, whether the aqueous solution satisfies the nitrite nitrogen concentration standard stipulated in the ministerial ordinance (Ministry of Health, Labor and Welfare Ordinance No. 15 on February 28, 2014) that amends part of the ministerial ordinance on water quality standards, etc. It becomes difficult.
In the analysis of nitrite nitrogen, the measurement of the next sample is not affected by other coexisting ion species, and in order to analyze anions simultaneously, the analysis time to sulfate ions can be completed within 30 minutes. Preferably it can be done.

The concentration of the aqueous solution containing sodium bicarbonate and sodium carbonate, as carbonate ion _(CO ^{3 2-)} combined concentration of sodium bicarbonate and sodium carbonate, it is 3.5mmol / L~12.0mmol / L Preferably, it is 3.5 mmol / L to 10 mmol / L, more preferably 4.5 mmol / L to 9.0 mmol / L.
If the carbonate ion (CO ₃ ²⁻ ) concentration of sodium bicarbonate and sodium carbonate combined is 3.5 mmol / L or more, the elution power of the mobile phase is not too weak and is within an appropriate range. The elution time of the nitrogen can be shortened, and other coexisting ion species in the sample are not eluted and remain in the column within the analysis time of one sample. Does not affect the measurement. In addition, if the carbonate ion (CO ₃ ²⁻ ) concentration of sodium bicarbonate and sodium carbonate combined is 12 mmol / L or less, the elution power of the mobile phase is not too strong and falls within an appropriate range. Since ions (Cl ⁻ ) and nitrite ions (NO ₂ ⁻ ) are sufficiently separated and eluted, nitrite nitrogen can be accurately quantified.

In the ion chromatography analysis method of nitrite nitrogen of the present invention, for example, an ion chromatograph as shown in FIG. 1 is used.
An ion chromatograph 100 shown in FIG. 1 includes a container 110, a flow pump 120, and a sample introduction provided in order along a direction in which an eluent 200 as a mobile phase flows (flow direction of the eluent 200). Unit 130, column 140, suppressor 150, and electrical conductivity detector 160. The container 110, the liquid pump 120, the sample introduction unit 130, the column 140, the suppressor 150, and the electrical conductivity detector 160 are connected to each other through a flow path 170 made of piping or the like.

An eluent 200 is accommodated in the container 110.
As the eluent 200, an aqueous solution containing the above sodium hydrogen carbonate and sodium carbonate is used.

The liquid flow pump 120 can send the eluent 200 in the container 110 at a constant flow rate.
The sample introduction unit 130 is provided in the middle of the flow path 170 that connects the liquid pump 120 and the column 140. A sample to be analyzed is introduced from the sample introduction unit 130 to the eluent 200 flowing through the flow path 170.

In the column 140, a housing (not shown) is filled with the above-described anion exchanger having a quaternary ammonium group as a filler. The column 140 separates ionic species including nitrite nitrogen (NO ₂ —N) contained in the sample.
The suppressor 150 ion-exchanges cations and hydrogen ions in the eluent 200 to change the composition of the eluent 200 to a composition having a low electrical conductivity.

The electrical conductivity detector 160 detects the ionic species separated by the column 140.
Moreover, in the ion chromatograph 100, the sample introduction part 130, the column 140, the suppressor 150, and the electrical conductivity detector 160 may be installed in a thermostat not shown. The thermostatic bath has a temperature control function and controls the temperature of the sample introduction unit 130, the column 140, the suppressor 150, and the electrical conductivity detector 160. Thereby, stable analysis can be performed.

  In the analysis using the ion chromatograph 100, the sample injected from the sample introduction unit 130 into the flow path 170 is guided to the column 140 by the eluent 200 that is passed through the flow path 170 by the liquid pump 120. It is burned. The column 140 separates ion species in the sample, and the separated ion species are measured by the electrical conductivity detector 160 as a change amount from the signal of the eluent 200 alone. The output signal from the electrical conductivity detector 160 is converted into a chromatogram by a data processing unit (not shown) connected to the electrical conductivity detector 160.

The flow rate of the eluent 200, that is, the mobile phase (the speed of flowing in the column 140) is not particularly limited, but is preferably 0.5 mL / min to 1.5 mL / min.
Moreover, the temperature of the column 140 when passing the mobile phase is not particularly limited, but is preferably 25 ° C to 60 ° C.

According to the ion chromatography analysis method of nitrite nitrogen of the present invention, an anion exchanger having a quaternary ammonium group is used as a column packing material, and an aqueous solution containing sodium hydrogen carbonate and sodium carbonate as a mobile phase , And the sodium hydrogen carbonate content in the aqueous solution is 2.0 to 7.5 times that of sodium carbonate in terms of molar ratio. In the conductivity detector, a low concentration of nitrite nitrogen ( NO ₂ —N) can be measured without being disturbed by chloride ions (Cl ⁻ ). That is, the ion chromatography analysis method of nitrite nitrogen of the present invention is 0.04 mg / min according to a ministerial ordinance (Ministry of Health, Labor and Welfare No. 15 on February 28, 2014) that revises a part of the ministerial ordinance on water quality standards. It is suitable as an analysis method for tap water in which the obligation to measure very low concentration of nitrite nitrogen (NO ₂ -N) of L or less is defined, and a quantitative accuracy of 0.004 mg / L or less can be realized.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

[Example 1]
As an ion chromatograph, a compact professional IC882 manufactured by Metrohm Japan Co., which incorporates an electrical conductivity detector and a suppressor was used.
As the column oven, CTO-20A manufactured by Shimadzu Corporation was used.
As a column, Shodex IC SI-35 4D (inner diameter 4.0 mm, manufactured by Showa Denko KK) packed with an anion exchanger (particle diameter 3.5 μm) made of a polyvinyl alcohol resin into which a quaternary ammonium group was introduced. A length of 150 mm and a housing material: polyetheretherketone resin were used.
As a mobile phase, an aqueous solution containing 4.0 mmol / L sodium hydrogen carbonate and 2.0 mmol / L sodium carbonate (sodium hydrogen carbonate content is 2.0 times that of sodium carbonate in molar ratio) was used.
The column temperature was maintained at 45 ° C., and the aqueous solution was passed through the column at a flow rate of 0.6 mL / min.
First, in ion-exchange water, nitrite ion (NO ₂ ⁻ ) is added to 0.003 mg / L (nitrite nitrogen (NO ₂ —N) formula amount 60 and nitrite ion (NO ₂ ⁻ ) formula amount 46; From this ratio, nitrite nitrogen (NO ₂ —N) corresponds to 0.004 mg / L.) 100 μL of the added blank sample was injected, and nitrite ions (NO ₂ ⁻ ) were detected. The elution time of nitrite ion (NO ₂ ⁻ ) was 7.31 minutes. The obtained chromatogram is shown in FIG. In FIG. 2, reference numeral 1 represents a peak of chloride ion (Cl ⁻ ) contained in the sodium nitrite aqueous solution used for the preparation of nitrite ion (NO ₂ ⁻ ), and reference numeral 2 represents nitrite ion (NO ₂ ). ₂ ^- shows the peak of). From the results of FIG. 2, it was confirmed that chloride ions (Cl ⁻ ) were detected at 5.7 minutes and nitrite ions (NO ₂ ⁻ ) were detected at 7.0 minutes.
Subsequently, chloride ion (Cl ⁻ ) is 100 mg / L and nitrite ion (NO ₂ ⁻ ) is 0.003 mg / L (nitrite nitrogen (NO ₂ —N)) in ion-exchanged water. 100 μL of a mixed sample to which 5 mg / L of sulfate ion (SO ₄ ²⁻ ) was added was injected, and nitrite ion (NO ₂ ⁻ ) was detected. The obtained chromatogram is shown in FIG. In FIG. 3, reference numeral 1 indicates a peak of chloride ion (Cl ⁻ ), and reference numeral 2 indicates a peak of nitrite ion (NO ₂ ⁻ ).
As the chloride ion (Cl ⁻ ), a sodium chloride aqueous solution (1000 mg / L standard reagent (made by Wako Pure Chemical Industries, Ltd.) as chloride ion (Cl ⁻ )) was used. As nitrite ions (NO ₂ ⁻ ), an aqueous sodium nitrite solution (1000 mg / L standard reagent (manufactured by Wako Pure Chemical Industries, Ltd.) as nitrite ions (NO ₂ ⁻ )) was used. As sulfate ion (SO ₄ ²⁻ ), an aqueous sodium sulfate solution (1000 mg / L standard reagent (manufactured by Wako Pure Chemical Industries, Ltd.) as sulfate ion (SO ₄ ²⁻ )) was used.

[Examples 2 to 5]
The analysis was performed in the same manner as in Example except that the concentration of sodium hydrogen carbonate and sodium carbonate and the amount ratio of sodium hydrogen carbonate and sodium carbonate were as shown in Table 1 as the mobile phase.

For Examples 1 to 5, elution time of chloride ions (Cl ⁻ ), nitrite ions (NO ₂ ⁻ ), sulfate ions (SO ₄ ²⁻ ), and nitrite ions (NO ₂ ⁻ ) in the mixed samples Table 1 shows the addition recovery rate. The nitrite ion (NO ₂ ⁻ ) addition recovery rate [%] in the mixed sample here means “nitrite ion (Cl ⁻ ) and sulfate ion (SO ₄ ²⁻ ) in the mixed sample ( NO ₂ ⁻ ) peak area] / [peak area of nitrite ion (NO ₂ ⁻ ) in the blank sample] × 100.

As can be seen from Table 1, in all of Examples 1 to 5, the addition recovery rate of nitrite ions (NO ₂ ⁻ ) in the mixed sample is 98.7% to 107.1%, and chloride ions (Cl ^-) without interference by, it was confirmed that quantification is possible for nitrite nitrogen (NO 2 _-N). In addition, the retention time of sulfate ion (SO ₄ ²⁻ ) was within 30 minutes, and it was confirmed that simultaneous analysis with other anions was possible.

[Comparative Example 1]
The same ion chromatograph, column oven, and column as in Example 1 were used.
As a mobile phase, an aqueous solution containing 4.0 mmol / L sodium bicarbonate and 2.5 mmol / L sodium carbonate (the content of sodium bicarbonate was 1.6 times that of sodium carbonate in terms of molar ratio) was used.
First, 100 μL of a blank sample in which 0.003 mg / L of nitrite ions (NO ₂ ⁻ ) (corresponding to 0.004 mg / L as nitrite nitrogen (NO ₂ —N)) was added to ion-exchanged water was injected. Nitrite ions (NO ₂ ⁻ ) were detected. The obtained chromatogram is shown in FIG. In FIG. 4, reference numeral 1 represents a peak of chloride ions (Cl ⁻ ) contained in the aqueous sodium nitrite solution used for the preparation of nitrite ions (NO ₂ ⁻ ), and reference numeral _{2 represents} nitrite ions (NO ₂ ). ₂ ^- shows the peak of).
Subsequently, in ion exchange water, chloride ion (Cl ⁻ ) is 100 mg / L, nitrite ion (NO ₂ ⁻ ) is 0.003 mg / L (nitrite nitrogen (NO ₂ —N) as 0.004 mg / L). 100 μL of a mixed sample to which 5 mg / L of sulfate ion (SO ₄ ²⁻ ) was added was detected, and nitrite ion (NO ₂ ⁻ ) was detected. The obtained chromatogram is shown in FIG. In FIG. 5, symbol 1 indicates a peak of chloride ion (Cl ⁻ ), and symbol 2 indicates a peak of nitrite ion (NO ₂ ⁻ ).

[Comparative Example 2]
The same ion chromatograph, column oven, and column as in Example 1 were used.
As a mobile phase, an aqueous solution containing 6.4 mmol / L sodium hydrogen carbonate and 0.8 mmol / L sodium carbonate (sodium hydrogen carbonate content is 8.0 times that of sodium carbonate in molar ratio) was used.
First, 100 μL of a blank sample in which 0.003 mg / L of nitrite ions (NO ₂ ⁻ ) (corresponding to 0.004 mg / L as nitrite nitrogen (NO ₂ —N)) was added to ion-exchanged water was injected. Nitrite ions (NO ₂ ⁻ ) were detected.
Subsequently, in ion exchange water, chloride ion (Cl ⁻ ) is 100 mg / L, nitrite ion (NO ₂ ⁻ ) is 0.003 mg / L (nitrite nitrogen (NO ₂ —N) as 0.004 mg / L). 100 μL of a mixed sample to which 5 mg / L of sulfate ion (SO ₄ ²⁻ ) was added was detected, and nitrite ion (NO ₂ ⁻ ) was detected.

For Comparative Example 1 and Comparative Example 2, the elution time of chloride ion (Cl ⁻ ), nitrite ion (NO ₂ ⁻ ), sulfate ion (SO ₄ ²⁻ ), and nitrite ion (NO ₂ ⁻ ) in the mixed sample Table 2 shows the addition recovery rate. The nitrite ion (NO ₂ ⁻ ) addition recovery rate [%] in the mixed sample here means “nitrite ion (Cl ⁻ ) and sulfate ion (SO ₄ ²⁻ ) in the mixed sample ( NO ₂ ⁻ ) peak area] / [peak area of nitrite ion (NO ₂ ⁻ ) in the blank sample] × 100.

As can be seen from Table 2, in Comparative Example 1, since the ratio of sodium hydrogen carbonate is low, the addition recovery rate of nitrite ion (NO ₂ ⁻ ) in the mixed sample is as low as 36.3%, and chloride ion (Cl ⁻ ), It was confirmed that nitrite nitrogen (NO ₂ —N) was difficult to determine.
In Comparative Example 2, it was difficult to distinguish the peak of nitrite nitrogen (NO ₂ —N) from the baseline.

DESCRIPTION OF SYMBOLS 100 ... Ion chromatograph, 110 ... Container, 120 ... Fluid pump, 130 ... Sample introduction part, 140 ... Column, 150 ... Suppressor, 160 ... Electrical conductivity detection 170, flow path, 200, eluent.

Claims (3)

While passing the mobile phase through the column filled with the packing material, the sample is introduced into the mobile phase, and the column contains ions containing nitrite nitrogen (NO ₂ -N) contained in the sample. An ion chromatography analysis method of nitrite nitrogen in which a species is separated and the separated ionic species is detected by an electrical conductivity detector,
The filler is an anion exchanger having a quaternary ammonium group;
The mobile phase is an aqueous solution containing sodium bicarbonate and sodium carbonate,
Content of the said sodium hydrogencarbonate in the said aqueous solution is 2.0 times-7.5 times of the said sodium carbonate in the said aqueous solution by molar ratio, The ion chromatography analysis method of nitrite nitrogen characterized by the above-mentioned.   The ion chromatographic analysis method of nitrite nitrogen according to claim 1, wherein the polymer substrate constituting the anion exchanger having a quaternary ammonium group is polyvinyl alcohol. The method for ion chromatography analysis of nitrite nitrogen according to claim 1 or 2, wherein the lower limit of quantification of the nitrite nitrogen (NO ₂ -N) is 0.004 mg / L or less.

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