Analysis method for measuring contents of formic acid and sulfamic acid by ion chromatography

Abstract

The invention belongs to the field of chemical analysis, and particularly relates to an analysis method for measuring the content of formic acid and sulfamic acid by ion chromatography, which comprises the following steps: (1) drawing a standard curve; (2) pretreatment of a sample to be detected; and (3) ion chromatography detection and analysis. The method for simultaneously determining formic acid and sulfamic acid is established through ion chromatography, and the analysis method is high in accuracy, good in stability, extremely high in detection efficiency, low in detection limit and wide in application range, and has applicability in the fields related to formic acid and sulfamic acid application such as electroplating polishing solutions, food, veterinary drugs and beverages.

Description

Technical Field

[0001] The invention belongs to the field of chemical analysis, and particularly relates to an analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography. Background Art

[0002] In the electroplating liquid industry, monitoring the composition and content of each component in the polishing liquid is an important part of controlling the plating liquid and improving the quality of electroplating. It is extremely important to measure the changes of each component in the polishing liquid at any time so as to replenish each component in time and adjust the solution to maintain the normal proportion of each component. However, the components of the electroplating liquid are complex, especially compared with the mixed acid of hydrofluoric acid, hydrochloric acid or nitric acid, which are widely used in various electroplating polishing acid baths but have strong acid corrosion and seriously pollute the environment. The existing technology has mostly used formic acid and aminosulfonic acid. At present, the method for determining the content of formic acid is mainly ion chromatography, and the methods for determining the content of aminosulfonic acid are mainly gas quantitative method, chemical titration method and capillary electrophoresis method. Most of these methods are cumbersome and time-consuming, the sample pretreatment is complicated, the reagents used do not meet the requirements of green environmental protection, and there are few reports on the simultaneous determination of aminosulfonic acid and formic acid.

[0003] In the literature, ion chromatography is used in series with a UV detector to achieve the determination of aminosulfonic acid and formic acid. The property of aminosulfonic acid that it has no UV response is used to perform qualitative and quantitative tests on aminosulfonic acid and formic acid through the conductivity and UV data subtraction method. The total value of the conductivity peaks of aminosulfonic acid and formic acid is detected respectively, and the formic acid is detected under the condition of 210nm by the series UV detector. The formic acid is quantitatively analyzed through the UV absorption peak of formic acid at a wavelength of 210nm, and the conductivity peak area value corresponding to formic acid is calculated from the formic acid concentration. The conductivity peak area value of formic acid is then deducted from the total conductivity peak area value of aminosulfonic acid and formic acid to obtain the conductivity peak area value of aminosulfonic acid, and then the aminosulfonic acid is quantitatively analyzed. The operation is complicated and the calculation process is cumbersome.

[0004] Ion chromatography is a chromatographic technology for separating anions and cations that has been developed in recent years. It is widely used in the electroplating industry. However, due to the complex composition of electroplating polishing liquid, the large number of products, and the mutual interference between the determination of each component, there are still certain obstacles to the direct qualitative and quantitative or even simultaneous determination of formic acid and aminosulfonic acid using ion chromatography. It also has problems such as high detection limit, low accuracy, and low detection efficiency. At the same time, it is not suitable for qualitative and quantitative analysis of the two organic acids in other fields involving the application of formic acid and aminosulfonic acid. Summary of the invention

[0005] In view of the defects of the prior art, the present invention discloses an analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography. The analytical method has high accuracy, good stability, extremely high detection efficiency, low detection limit, and a wide range of applications. The method is applicable to the fields involving the application of formic acid and aminosulfonic acid, such as electroplating polishing liquid, food, veterinary drugs, and beverages.

[0006] The present invention provides an analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography, the method comprising the following steps:

[0007] (1) Drawing of a standard curve: preparing a mixed standard solution of a formic acid standard and an aminosulfonic acid standard, performing ion chromatography on the mixed standard solution to obtain a standard concentration, and making a standard curve to obtain a regression equation for each standard;

[0008] (2) Pretreatment of the sample to be tested: pretreating the sample to be tested to obtain a sample solution;

[0009] (3) Ion chromatography detection and analysis: The sample solution was subjected to ion chromatography detection to obtain a liquid chromatogram of the sample solution. The type of organic acid was determined based on the peak positions of the formic acid standard and the aminosulfonic acid standard. The content of the organic acid was then calculated based on the regression equation of each standard.

[0010] In some embodiments of the present invention, the pre-treatment sequentially comprises dissolution and dilution, purification and filtration.

[0011] In the prior art, the analysis of formic acid and aminosulfonic acid in various systems often requires a variety of means. For example, there is a document that uses an ion chromatography in series with an ultraviolet detector to determine aminosulfonic acid and formic acid. The property of aminosulfonic acid that it has no ultraviolet response is used to qualitatively and quantitatively determine aminosulfonic acid and formic acid by conductivity and ultraviolet data subtraction. However, due to the complexity of the pre-treatment means and data processing steps, the accuracy cannot be quickly and accurately quantified. Based on this, the present invention proposes an analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography, which realizes efficient and accurate simultaneous quantitative analysis of formic acid and aminosulfonic acid by specific pre-treatment steps and ion chromatography detection conditions.

[0012] In some embodiments of the present invention, the pre-treatment comprises dissolution, dilution, purification and filtration.

[0013] In some embodiments of the present invention, the pre-treatment comprises dissolving and diluting with deionized water, purifying with a solid phase extraction column and filtering with a filter membrane.

[0014] Preferably, the dissolving and diluting with deionized water is diluted to 100 to 2000 times.

[0015] In some embodiments of the present invention, the step of purifying by solid phase extraction column is: pre-treating the pretreatment column and the purification column respectively, then connecting the pretreatment column and the purification column in series, and finally passing the diluted sample to be tested through the pretreatment column and the purification column in sequence.

[0016] Preferably, the pretreatment in the step of purification by solid phase extraction column is to inject ultrapure water, keep the ultrapure water level higher than the filler in the column by ≥1 mm, and let it stand for 20 to 60 minutes.

[0017] Preferably, the pretreatment column is a C18 solid phase extraction column.

[0018] Preferably, the flow rate through the pretreatment column is 0.1 to 0.3 drops / s.

[0019] Preferably, the purification column is an On-Guard II H and / or On-Guard II Na column.

[0020] Preferably, the flow rate through the purification column is 0.2 to 0.3 drops / s.

[0021] Preferably, the filter membrane has a pore size of 0.22 μm or 0.45 μm.

[0022] In the prior art, interference from alkaline earth metal ions and transition metal ions often exists in sample systems containing formic acid and aminosulfonic acid. The present invention significantly reduces the interference from impurities through a specific pretreatment step, by dissolving and diluting with deionized water, purifying with a series of solid phase extraction columns, and then filtering with a filter membrane. The pretreatment step is simple and efficient.

[0023] In some embodiments of the present invention, the ion chromatography detection selects a self-generated cycle suppressed conductivity detector.

[0024] The present invention uses a self-generated circulation suppression conductivity detector, the standard product has higher sensitivity, the obtained linear curve is better, and the quantitative accuracy of ion chromatography detection is increased.

[0025] In some embodiments of the present invention, the suppressor current is 3-15 mA.

[0026] In some embodiments of the present invention, the eluent is a sodium hydroxide and / or potassium hydroxide solution.

[0027] In some embodiments of the present invention, the concentration of the eluent is 0.5-4 mmol / L.

[0028] In some embodiments of the present invention, the flow rate of the eluent is 0.4-1.2 mL / min.

[0029] The principle of ion exchange chromatography is to use ion exchange resin as the stationary phase, which has fixed ion groups and exchangeable ion groups. When the eluent carries the ions generated by the ionization of the components through the stationary phase, the component ions and the exchangeable ion groups on the resin undergo reversible transformation, and are finally separated according to the different affinities of the component ions to the resin. When the concentration of sodium hydroxide and / or potassium hydroxide solution in the eluent increases, the ion exchange rate generally increases, which in turn causes the peak time of each component to be advanced, affecting the separation degree of each component. The present invention limits the type, concentration and flow rate of the eluent, and specially sets the current range of the ion chromatography suppressor. Under the coordinated processing and detection, the rapid and efficient separation of formic acid and aminosulfonic acid is achieved, and the synchronous quantification of formic acid and aminosulfonic acid is achieved.

[0030] In the prior art, when using ion chromatography to detect the content of formic acid or aminosulfonic acid, the eluent concentration set by the ion chromatography is mostly a high concentration of inorganic base, which limits the separation process of the organic acid to be tested; at the same time, when using ion chromatography to detect the content of formic acid or aminosulfonic acid, it is limited by the pretreatment and detection method, and its detection limit is often very high. This type of detection and analysis method is obviously not suitable for the accurate quantification of samples with less content, and often requires more detection instruments and steps, with high cost and poor universality. The present invention, by limiting the suppressor current, avoids the problem of baseline elevation caused by improper current setting, which in turn causes the noise to increase and the detection limit to increase, and further improves the analysis and detection efficiency.

[0031] In some embodiments of the present invention, the conditions for the ion chromatography detection are as follows: the separation column is AS18 (4 mm×250 mm), the guard column is AG18 (4 mm×50 mm), and the injection volume is 4000-5500 μL.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention provides a method for simultaneously determining formic acid and aminosulfonic acid. The method has high accuracy, good stability, extremely high detection efficiency, low detection limit, and a wide range of applications. It can be applied to systems containing formic acid and aminosulfonic acid commonly used in the prior art, and can achieve efficient and accurate quantitative analysis.

[0034] (2) The present invention realizes the simultaneous detection of aminosulfonic acid and formic acid by adjusting the elution concentration of the eluent, thereby achieving effective separation and accurate quantification, with high detection efficiency. In addition, the detection limits of aminosulfonic acid and formic acid in this method are low, both of which are 20 μg / L, and the universality is extremely high.

[0035] (3) The method disclosed in the present invention can achieve rapid and accurate qualitative and quantitative analysis with high reliability and simple detection and data processing. The content of formic acid and aminosulfonic acid in the sample to be tested can be directly obtained through the standard curve on the instrument, which solves the disadvantage of the prior art that a large number of cumbersome calculation processes are required, reduces the errors that may exist in the data processing process, and greatly improves the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a typical chromatogram of the separation of formic acid and aminosulfonic acid in Example 1 (200 μg / L).

[0037] Figure 2 This is the chromatogram of the polishing liquid sample in Example 1.

[0038] Figure 3 It is the chromatogram of the veterinary drug sample in Example 6. DETAILED DESCRIPTION

[0039] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0040] In the descriptions of the examples and comparative examples of the present invention, the reagents can be easily obtained from commercial companies.

[0041] Example 1

[0042] An analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography, the method comprising the following steps:

[0043] (1) Drawing of standard curve: According to Table 1, formic acid standard and aminosulfonic acid standard were taken, diluted with water to form a standard stock solution containing 1000 mg / L, and then diluted with the standard stock solution to prepare standard solutions of 20 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L, 1000 μg / L, and 2000 μg / L, and the calibration curves of mass concentration and peak area of ​​formic acid and aminosulfonic acid were drawn:

[0044] Formic acid: standard curve is y=0.001X+0.0119, R 2 =0.9997;

[0045] Aminosulfonic acid: standard curve is y=0.0008X-0.0029, R 2 =1;

[0046] According to the selected chromatographic conditions, the typical chromatogram of formic acid and aminosulfonic acid separation (200 μg / L) is as follows Figure 1 As shown by Figure 1 It can be seen that the retention time of formic acid is 9.261min, and the retention time of aminosulfonic acid is 9.827min;

[0047] (2) Pretreatment of the sample to be tested: The polishing liquid sample is dissolved and diluted with deionized water to a concentration of less than 10 ppm, passed through a solid phase extraction column, and then filtered through a 0.45 μm filter membrane to obtain an on-machine polishing liquid sample solution;

[0048] (3) Ion chromatography detection and analysis: The polishing liquid sample solution is subjected to ion chromatography detection to obtain a liquid chromatogram of the sample solution, and the type of organic acid is determined according to the peak positions of the formic acid standard and the aminosulfonic acid standard, and then the content of the organic acid is calculated according to the regression equation of each standard;

[0049] The ion chromatography detection used was a self-generated circulating suppressed conductivity detector, the suppressor current was 10 mA, the eluent was 2 mmol / L sodium hydroxide solution, and the eluent flow rate was 0.8 mL / min;

[0050] The steps of the solid phase extraction column purification are as follows: inject 20 mL of ultrapure water into the C18 solid phase extraction column, On-Guard II H and On-Guard II Na columns in series respectively with a syringe, keep the ultrapure water level above the filler in the column by 1 mm, let it stand for 40 minutes, and then connect them in series in sequence, and finally pass the diluted sample to be tested through the C18 solid phase extraction column (the flow rate is 0.2 drops / s), On-Guard II H and On-Guard II Na columns (the flow rate is 0.3 drops / s) in sequence;

[0051] The separation column used was AS18 (4 mm × 250 mm), the guard column was AG18 (4 mm × 50 mm), and the injection volume was 5500 μL.

[0052] like Figure 2 As shown, this method can effectively separate and qualitatively identify formic acid and aminosulfonic acid in the polishing liquid. The retention time is 11.441 min for formic acid and 12.117 min for aminosulfonic acid. The peak response is high and the baseline at the peak position is relatively stable. The quantitative results of ion chromatography analysis are shown in Table 2.

[0053] Example 2

[0054] An analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography, the specific steps are the same as those in Example 1, except that the suppressor current used is 2 mA, and the quantitative results of the ion chromatography analysis are shown in Table 2.

[0055] Example 3

[0056] An analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography, the specific steps are the same as those in Example 1, except that the suppressor current used is 16 mA, and the quantitative results of the ion chromatography analysis are shown in Table 2.

[0057] Example 4

[0058] An analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography, the specific steps are the same as those in Example 1, except that the concentration of the eluent used is 4.5 mmol / L. The quantitative results of the ion chromatography analysis are shown in Table 2.

[0059] Example 5

[0060] An analytical method for determining the content of formic acid and aminosulfonic acid by ion chromatography, the specific steps are the same as those in Example 1, except that the flow rate of the eluent used is 1.3 mL / min, and the quantitative results of the ion chromatography analysis are shown in Table 2.

[0061] Example 6

[0062] An analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography, the method comprising the following steps:

[0063] (1) The drawing of the standard curve is the same as in Example 1;

[0064] (2) Pretreatment of the sample to be tested: The veterinary drug sample is dissolved and diluted with deionized water to less than 10 ppm, passed through a solid phase extraction column, and then filtered through a 0.45 μm filter membrane to obtain an on-machine veterinary drug sample solution;

[0065] (3) Ion chromatography detection and analysis: The sample solution is subjected to ion chromatography detection to obtain a liquid chromatogram of the sample solution, and the type of organic acid is determined according to the peak positions of the formic acid standard and the aminosulfonic acid standard, and the content of the organic acid is calculated according to the regression equation of each standard;

[0066] The ion chromatography detection used was a self-generated circulating suppressed conductivity detector, the suppressor current was 7 mA, the eluent was 3 mmol / L potassium hydroxide solution, and the eluent flow rate was 1 mL / min;

[0067] The step of purification through the solid phase extraction column is: inject 20mL of ultrapure water into the C18 solid phase extraction column, On-Guard II H and On-Guard II Na columns in series respectively with a syringe, keep the ultrapure water level above the filler in the column by 1mm, let it stand for 40 minutes, and then connect them in series in sequence, and finally pass the diluted sample to be tested through the C18 solid phase extraction column (the flow rate is 0.2 drops / s), On-Guard II H and On-Guard II Na columns (the flow rate is 0.3 drops / s) in sequence;

[0068] The separation column used was AS18 (4 mm × 250 mm), the guard column was AG18 (4 mm × 50 mm), and the injection volume was 5000 μL.

[0069] like Figure 3 As shown, this method can effectively separate formic acid and aminosulfonic acid in qualitative veterinary drugs. The retention time is 11.504min for formic acid and 12.217min for aminosulfonic acid. The peak response is high and the baseline at the peak position is relatively stable. The qualitative and quantitative results of ion chromatography analysis are shown in Table 3.

[0070] Table 1

[0071]

[0072] Table 2 Ion chromatography analysis results of formic acid and aminosulfonic acid of polishing liquid samples

[0073]

[0074] Table 3 Ion chromatography analysis results of formic acid and aminosulfonic acid in veterinary drug samples

[0075]

[0076] It can be seen from the results of the above-mentioned Examples 1 and 6 that the analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography disclosed in the present invention can effectively distinguish formic acid and aminosulfonic acid by dissolving and diluting the polishing liquid and veterinary drug samples and then detecting and analyzing them by ion chromatography, and determining the type of organic acid according to the peak position of each standard product, thereby achieving separation and qualitative analysis, and then using the regression equation of each standard product to calculate the contents of formic acid and aminosulfonic acid. Compared with Examples 2-5, the deviation between the measured value and the theoretical value of Example 1 is small, and the recovery rate is high, indicating that the analytical method provided by the present invention can obtain quantitative results of formic acid and aminosulfonic acid more accurately and simultaneously, and greatly shorten the analysis time.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography, characterized in that: The method comprises the following steps: (1) Drawing of a standard curve: preparing a mixed standard solution of a formic acid standard and an aminosulfonic acid standard, performing ion chromatography on the mixed standard solution to obtain a standard concentration, and making a standard curve to obtain a regression equation for each standard; (2) Pretreatment of the sample to be tested: pretreating the sample to be tested to obtain a sample solution; (3) Ion chromatography detection and analysis: The sample solution was subjected to ion chromatography detection to obtain a liquid chromatogram of the sample solution. The type of organic acid was determined based on the peak positions of the formic acid standard and the aminosulfonic acid standard. The content of each organic acid was then calculated based on the regression equation of each standard.

2. The analytical method for measuring formic acid and aminosulfonic acid content by ion chromatography according to claim 1, characterized in that: The pre-treatment includes dissolution, dilution, purification and filtration in sequence.

3. The analytical method for measuring formic acid and aminosulfonic acid content by ion chromatography according to claim 2, characterized in that: The pretreatment comprises dissolving and diluting with deionized water, purifying with a solid phase extraction column and filtering with a filter membrane.

4. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 3, characterized in that: The steps of purification through solid phase extraction column are: pre-treating the pretreatment column and the purification column respectively, then connecting the pretreatment column and the purification column in series, and finally passing the diluted sample to be tested through the pretreatment column and the purification column in sequence.

5. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, characterized in that: The ion chromatography detection selects a self-generated circulation suppression conductivity detector.

6. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, characterized in that: The suppressor current is 3-15 mA.

7. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, characterized in that: The eluent is sodium hydroxide and / or potassium hydroxide solution.

8. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, characterized in that: The concentration of the eluent is 0.5-4 mmol / L.

9. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, characterized in that: The flow rate of the eluent is 0.4-1.2 mL / min.

10. The analytical method for determining the contents of formic acid and aminosulfonic acid by ion chromatography according to claim 1, wherein The characteristic is that the conditions of the ion chromatography detection are as follows: the separation column is AS18, the protection column is AG18, Injection volume 4000~5500μL.

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