Method for simultaneously measuring water-soluble organic acid and inorganic anion

Abstract

The invention relates to the technical field of environmental monitoring and analytical testing, and provides a method for simultaneously measuring water-soluble organic acid and inorganic anions. According to the method, the to-be-detected solution is detected through ion chromatography, the KOH solution is adopted as the leacheate, and the gradient leaching procedure is reasonably designed, so that organic acids and inorganic anions with different polarities can obtain better separation degree, the peak shape is improved, and the detection sensitivity is improved; therefore, the water-soluble organic acid and the inorganic anions are separated and measured in the same ion chromatography system at the same time, and the detection efficiency is remarkably improved. Moreover, the method provided by the invention has relatively strong applicability, is not only suitable for determining the water-soluble components in the atmospheric fine particulate matter sample, but also can be applied to rainwater, fog water and other aqueous solution systems, and has accurate and reliable results and relatively high popularization value.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring and analysis testing technology, and in particular to a method for simultaneously measuring water-soluble organic acids and inorganic anions. Background Technology

[0002] Fine particulate matter (PM2.5) refers to particulate matter with an aerodynamic equivalent diameter of 2.5 micrometers or less, characterized by its small size, large specific surface area, and long residence time in the atmosphere. PM2.5 not only penetrates deep into the respiratory system, posing a threat to human health, but also plays a significant role in reducing atmospheric visibility, contributing to regional haze formation, and influencing climate change. Therefore, accurately determining the chemical composition of PM2.5 is crucial for assessing atmospheric environmental quality and controlling pollution. Water-soluble components of PM2.5 typically constitute a large proportion of its total mass, with inorganic anions (such as SO42-) being the most abundant. 2- NO3 - Cl - (etc.) are among the most important components. These anions not only reflect the acid-base balance in the atmosphere, but are also closely related to the formation process of secondary aerosols, and are important indicators for studying the chemical mechanisms of air pollution.

[0003] Besides inorganic anions, water-soluble organic acids (such as formic acid, acetic acid, oxalic acid, and other low-molecular-weight carboxylic acids) are also commonly found in PM2.5. Their sources include primary emissions and secondary transformation processes, and they have a significant impact on particulate matter acidity regulation, secondary organic aerosol formation, and atmospheric chemical reactions. Compared to inorganic anions, organic acids are more diverse, have lower concentrations, and are more difficult to detect; therefore, related research and monitoring methods still need improvement.

[0004] Currently, methods for determining fine particulate matter components mainly include ion chromatography, gas chromatography, and high-performance liquid chromatography. Among these, ion chromatography has become the most commonly used method due to its simplicity, high sensitivity, and suitability for the analysis of water-soluble components. However, because there are many types of organic acids with significant differences in polarity and retention characteristics, current ion chromatography methods often struggle to achieve effective separation of multiple components, leading to peak overlap and insufficient quantitative accuracy. Therefore, water-soluble organic acids often require separate methods for determination and cannot be analyzed simultaneously with inorganic anions. Summary of the Invention

[0005] In view of this, the present invention provides a method for simultaneously measuring water-soluble organic acids and inorganic anions. The method provided by the present invention is the first to achieve the simultaneous determination of water-soluble organic acids and inorganic anions in a single ion chromatography detection, significantly improving detection efficiency and avoiding errors caused by multiple injections.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for simultaneously measuring water-soluble organic acids and inorganic anions includes the following steps: The test solution was subjected to ion chromatography to obtain a chromatogram; qualitative and quantitative analysis was performed based on the chromatogram to obtain the types and concentrations of water-soluble organic acids and inorganic anions in the test solution; The water-soluble organic acids include formic acid, acetic acid, methanesulfonic acid, oxalic acid, succinic acid, and glutaric acid; the inorganic anions include F... - Cl - NO3 - SO4 2- and PO4 3- ; The eluent used in the ion chromatography detection is KOH solution, and the elution method is gradient elution. The elution program of the gradient elution is as follows: the eluent concentration is 1.5~2.5 mM from 0 min to 10 min, the eluent concentration increases from 1.5~2.5 mM to 29.5~30.5 mM from 10 min to 24 min, the eluent concentration is maintained at 29.5~30.5 mM from 24 min to 27 min, and the eluent concentration decreases to 1.5~2.5 mM from 27 min to 35 min.

[0007] Preferably, the test liquid is a fine particulate extract, rainwater, or mist.

[0008] Preferably, the method for preparing the fine particulate matter extract is as follows: sampling fine particulate matter using a filter membrane to obtain a sampling filter membrane; and extracting the sampling filter membrane to obtain the fine particulate matter extract.

[0009] Preferably, the filter membrane is a quartz filter membrane; before sampling, the filter membrane is further pretreated; the pretreatment includes heating the filter membrane; the heating temperature is 550°C and the time is 5.5 hours; the sampling is performed using an atmospheric particulate matter sampler.

[0010] Preferably, the extraction agent used in the extraction process is deionized water; the extraction process is carried out under ultrasonic oscillation conditions, and the extraction time is 20-30 minutes.

[0011] Preferably, before performing ion chromatography detection on the test solution, the chromatographic column is further rinsed; the rinsing includes: first rinsing with a KOH solution with a concentration of 29.5~30.5 mM for 25~35 min, and then rinsing with a KOH solution with a concentration of 1.5~2.5 mM for 25~35 min.

[0012] Preferably, the qualitative analysis includes: determining the types of water-soluble organic acids and inorganic anions in the test solution based on the retention times of the chromatographic peaks in the chromatogram.

[0013] Preferably, the quantification includes: determining the concentrations of water-soluble organic acids and inorganic anions in the test solution using a standard curve based on the height or peak area of ​​each chromatographic peak in the chromatogram; the standard curve is a curve showing the relationship between peak area or peak height and the concentration of the target component.

[0014] Preferably, the method for plotting the standard curve includes: preparing a series of mixed standard solutions using water-soluble organic acids and inorganic anionic standards, performing ion chromatography detection on the series of mixed standard solutions, and plotting the standard curve based on the detection results.

[0015] Preferably, when the test solution is a fine particulate matter extract, after obtaining the concentrations of water-soluble organic acids and inorganic anions in the test solution, the method further includes calculating the concentrations of water-soluble organic acids and inorganic anions in the atmosphere using Formula I. Formula I; In Equation I, C represents the concentration of the target component in the atmosphere, in μg / m³. 3 C sample and C blank These represent the concentrations of the corresponding components in the leachate of the sample and blank filter membrane, respectively, in mg / L, and V is the sampling volume, in m³. 3 R is the area conversion factor.

[0016] This invention provides a method for simultaneously measuring water-soluble organic acids and inorganic anions, comprising the following steps: performing ion chromatography on the test solution to obtain a chromatogram; performing qualitative and quantitative analysis based on the chromatogram to obtain the types and concentrations of water-soluble organic acids and inorganic anions in the test solution; wherein the water-soluble organic acids include formic acid, acetic acid, methanesulfonic acid, oxalic acid, succinic acid, and glutaric acid; and the inorganic anions include F... - Cl - NO3 - SO4 2- and PO4 3-The ion chromatography detection uses KOH solution as the eluent, and the elution method is gradient elution. The gradient elution program is as follows: from 0 min to 10 min, the eluent concentration is 1.5–2.5 mM; from 10 min to 24 min, the eluent concentration increases from 1.5–2.5 mM to 29.5–30.5 mM; from 24 min to 27 min, the eluent concentration is maintained at 29.5–30.5 mM; and from 27 min to 35 min, the eluent concentration decreases to 1.5–2.5 mM. This invention uses KOH solution as the eluent, and through a rationally designed gradient elution program, it can achieve better separation of organic acids and anions of different polarities, improve peak shape, and thus significantly improve separation efficiency and detection sensitivity. This invention enables the simultaneous separation and determination of water-soluble organic acids and inorganic anions in PM2.5 samples in the same ion chromatography system, significantly improving detection efficiency and avoiding errors caused by multiple injections. Furthermore, the method provided by this invention has strong applicability. It is not only applicable to the determination of water-soluble components in atmospheric fine particulate matter samples, but also applicable to rainwater, fog water and other aqueous solution systems. The results are accurate and reliable, and it has high promotional value. Attached Figure Description

[0017] Figure 1 The chromatogram obtained in Example 1; Figure 2 The chromatogram obtained in Comparative Example 1; Figure 3 The chromatogram is that of Comparative Example 2. Detailed Implementation

[0018] This invention provides a method for simultaneously measuring water-soluble organic acids and inorganic anions, comprising the following steps: The test solution was subjected to ion chromatography to obtain a chromatogram; qualitative and quantitative analysis was performed based on the chromatogram to obtain the types and concentrations of water-soluble organic acids and inorganic anions in the test solution; The water-soluble organic acids include formic acid (FA), acetic acid (AA), methanesulfonic acid (MSA), oxalic acid (OA), succinic acid (SA), and glutaric acid (GA); the inorganic anions include F - Cl - NO3 - SO4 2- and PO4 3- ; The eluent used in the ion chromatography detection is KOH solution, and the elution method is gradient elution. The elution program of the gradient elution is as follows: the eluent concentration is 1.5~2.5 mM from 0 min to 10 min, the eluent concentration increases from 1.5~2.5 mM to 29.5~30.5 mM from 10 min to 24 min, the eluent concentration is maintained at 29.5~30.5 mM from 24 min to 27 min, and the eluent concentration decreases to 1.5~2.5 mM from 27 min to 35 min.

[0019] In this invention, the test liquid is preferably a fine particulate extract, rainwater, or mist.

[0020] In this invention, the preferred method for preparing the fine particulate matter extract is as follows: sampling fine particulate matter using a filter membrane to obtain a sampling filter membrane; extracting the sampling filter membrane to obtain a fine particulate matter extract; the fine particulate matter is PM2.5; the filter membrane is preferably a quartz filter membrane, specifically a Whatman quartz filter membrane with a diameter of 47 mm. Before sampling, it is preferable to further pre-treat the filter membrane; the pre-treatment preferably includes: heating the filter membrane; the heating temperature is preferably 550°C, and the time is preferably 5.5 h; this invention removes background organic matter from the filter membrane through heating treatment; after heating treatment, the filter membrane is preferably cooled and then stored under clean conditions for later use. The sampling is preferably performed using an atmospheric particulate matter sampler, preferably a four-channel sampler, model TH-16A. The sampling point is preferably located 15m above the ground, with no significant interfering buildings nearby. The sampling flow rate is preferably 16.7 L / min, and the sampling time is preferably 24 hours. In a specific embodiment of the invention, sampling is preferably performed from 8:00 am to 8:00 am the following day. In a specific embodiment of the invention, the pretreated filter membrane is preferably installed in the atmospheric particulate matter sampler, and PM2.5 samples are collected at the set flow rate and sampling time. After sampling, the filter membrane is removed, sealed, and frozen in a low-temperature environment until analysis; the freezing temperature is preferably -4°C. In a specific embodiment of the invention, during freezing, the filter membrane is preferably placed in a clean filter membrane box and wrapped with aluminum foil to reduce secondary pollution and volatilization of organic matter.

[0021] In this invention, the extraction agent used in the extraction process is preferably deionized water, and the resistivity of the deionized water is preferably ≥18.2 MΩ·cm. The extraction process is preferably carried out under ultrasonic oscillation conditions, specifically in an ultrasonic cleaner. In a specific embodiment of this invention, the ultrasonic cleaner shown is model KQ5200DE (Kunshan Shumei). The extraction time is preferably 20~30 min. Before the extraction process, the sampling filter membrane is preferably cut into circular pieces, placed in a clean centrifuge tube, and then deionized water is added. The sample is then ultrasonically oscillated in an ultrasonic cleaner for 20~30 min to fully dissolve the water-soluble components in the particulate matter. The diameter of the circular pieces is preferably 17 mm. After ultrasonic oscillation, the oscillated sample solution is preferably filtered using a disposable needle filter (0.22 μm pore size, Tianjin Jinteng) to obtain the filtrate as the test solution. If necessary, the supernatant of the oscillated sample solution can also be obtained by centrifugation as the test solution.

[0022] In this invention, the chromatographic column used for the ion chromatography detection is preferably an AS11 column (4 mm, Thermo).

[0023] In this invention, before performing ion chromatography detection on the test solution, it is preferable to further rinse the chromatographic column; the rinsing preferably includes: first rinsing with a KOH solution of concentration of 29.5~30.5 mM for 25~35 min, and then rinsing with a KOH solution of concentration of 1.5~2.5 mM for 25~35 min. In a specific embodiment of this invention, it is preferable to first rinse with a KOH solution of concentration of 30 mM for 30 min, and then rinse with a KOH solution of concentration of 2 mM for 30 min. In this invention, the chromatographic column is first rinsed with a high concentration of eluent to remove residues, and then the eluent of the initially set concentration is switched to rinse until the baseline is stable, so as to ensure that the chromatographic column is in a stable state.

[0024] In this invention, the eluent used in the ion chromatography detection is a KOH solution, and the elution method is gradient elution. The gradient elution includes: from 0 min to 10 min, the eluent concentration is 1.5–2.5 mM, preferably 2 mM; from 10 min to 24 min, the eluent concentration increases from 1.5–2.5 mM to 29.5–30.5 mM, preferably from 2 mM to 30 mM; from 24 min to 27 min, the eluent concentration is maintained at 29.5–30.5 mM, preferably 30 mM; and from 27 min to 35 min, the eluent concentration decreases to 1.5–2.5 mM, preferably from 30 mM to 2 mM. In a specific embodiment of this invention, after the column is rinsed, the anion electrolysis self-regenerating suppressor is preferably activated, adjusted to an appropriate suppression current and regeneration mode, and a gradient elution program is set. In this invention, the regeneration mode is preferably the AutoSuppression regeneration recovery mode, and the suppression current is preferably 5–80 mA, in this embodiment it is 70–80 mA.

[0025] In this invention, the detection time for each sample is preferably 35 min, and the injection volume is preferably 1 mL.

[0026] In this invention, the test solution is preferably filtered through a microporous membrane and then placed into a sample vial, and injected into an ion chromatograph at a set volume using an autosampler for analysis; in a specific embodiment of this invention, a 1 mL syringe can be used to extract the test solution, install a filter membrane, and then inject it into an ion chromatograph for analysis and measurement.

[0027] In this invention, after obtaining the chromatogram, qualitative and quantitative analysis is performed based on the chromatogram to obtain the types and concentrations of water-soluble organic acids and inorganic anions in the test solution. The qualitative analysis preferably includes: determining the types of water-soluble organic acids and inorganic anions in the test solution based on the retention times of the chromatographic peaks in the chromatogram. In a specific embodiment of this invention, it is preferable to prepare separate standard solutions of water-soluble organic acids and inorganic anions, and perform ion chromatography detection according to the above scheme to determine the retention times of each standard. Based on the retention times of each chromatographic peak in the chromatogram and the retention times of the standards, the components corresponding to each peak in the test solution are determined to achieve qualitative analysis.

[0028] In this invention, the quantitative method preferably includes: determining the concentrations of water-soluble organic acids and inorganic anions in the test solution using a standard curve based on the height or peak area of ​​each chromatographic peak in the chromatogram; the standard curve is a curve showing the relationship between peak area or peak height and the concentration of the target component; specifically, the vertical axis of the standard curve represents the peak area or peak height of the water-soluble organic acid or inorganic anion, and the horizontal axis represents the concentration of the water-soluble organic acid or inorganic anion.

[0029] In this invention, the preferred method for plotting the standard curve includes: preparing a series of mixed standard solutions using water-soluble organic acids and inorganic anionic standards; performing ion chromatography detection on the series of mixed standard solutions; and plotting the standard curve based on the detection results. The ion chromatography conditions for plotting the standard curve are the same as those described above and will not be repeated here.

[0030] In this invention, the standard curves include water-soluble organic acid standard curves and inorganic anion standard curves; the water-soluble organic acid standard curves specifically include FA standard curves, AA standard curves, MSA standard curves, OA standard curves, SA standard curves, and GA standard curves; the inorganic anion standard curves specifically include F... - Standard curve, Cl - Standard curve, NO3 - Standard curve, SO4 2- Standard curve and PO4 3- Standard curves; the concentration range of the FA, AA, MSA, GA, and SA standard curves is preferably 0~1 mg / L, F - Cl - The preferred concentration range for OA is 0~10 mg / L, and for NO3... - SO4 2- The preferred concentration range for the standard curve is 0–50 mg / L, PO4 3- The concentration range of the standard curve is preferably 0~20 mg / L; the uncertainty of each standard is 0.5%.

[0031] In this invention, the series of mixed standard solutions includes seven concentration gradients of mixed standard solutions, denoted as the first mixed standard solution to the seventh mixed standard solution. The concentrations of FA, AA, MSA, GA, and SA in the first to seventh mixed standard solutions are 0.01, 0.03, 0.05, 0.1, 0.3, 0.5, and 1 mg / L, respectively. - Cl - The concentrations of OA were 0.1 mg / L, 0.3, 0.5, 1, 3, 5, and 10 mg / L, respectively, and NO3... - SO4 2- The concentrations were 0.5, 1.5, 2.5, 5, 15, 25, and 50 mg / L, respectively, for PO4. 3- The concentrations were 0.2, 0.6, 1, 2, 6, 10, and 20 mg / L, respectively. Preferably, the mixed standard series solutions were subjected to chromatographic detection under the same conditions, the peak area or peak height of each component was recorded, and a standard curve of concentration versus peak area or peak height was plotted.

[0032] In this invention, qualitative and quantitative analysis using the standard curve method is based on the following principle: In ion chromatography analysis, different components have relatively constant elution times under set elution conditions, which can be used to determine the type of substance; at the same time, the peak area or peak height of a component has a good linear relationship with its concentration. By preparing a series of standard solutions with known concentrations, and injecting them under the same gradient elution conditions, the elution time and peak area (or peak height) of each component are recorded, and a standard curve of concentration versus peak area (or peak height) is plotted. The peak area of ​​each component in the test solution can be substituted into the standard curve for interpolation calculation to obtain the concentration of each component.

[0033] In this invention, when the test solution is a fine particulate matter extract, after obtaining the concentrations of water-soluble organic acids and inorganic anions in the test solution, the method further includes calculating the concentrations of water-soluble organic acids and inorganic anions in the atmosphere using Formula I. Formula I; In Equation I, C represents the concentration of the target component in the atmosphere, in μg / m³. 3 C sample and C blank These represent the concentrations of the corresponding components in the leachate of the sample and blank filter membrane, respectively, in mg / L, and V is the sampling volume, in m³. 3 R is the area conversion factor.

[0034] In this invention, the area conversion factor R varies depending on the experimental equipment. Different detection instruments and sampling instruments will affect this factor. In the specific implementation of this invention, the area conversion factor can be determined according to the actual situation.

[0035] In this invention, the concentration of the corresponding component in the blank filter membrane is obtained by extracting and detecting the blank filter membrane using the same method, which will not be described in detail here.

[0036] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] In the embodiments of the present invention, all tests without specified temperatures were conducted at room temperature.

[0038] Example 1 This embodiment detects water-soluble organic acids and inorganic anions in fine particulate matter. The specific steps are as follows: (1) Before sampling, the quartz filter membrane (Whatman, diameter 47 mm) was placed in a muffle furnace and heated at 550°C for 5.5 h to remove organic matter from the background of the filter membrane.

[0039] (2) The pretreated filter membrane was placed into a four-channel sampler (Wuhan Tianhong, TH-16A) for sampling. The flow rate was 16.7 L / min. To ensure that the sample volume met the requirements for analysis, the sampling time was 24 hours (8:00 am to 8:00 a.m. the next day). (3) Use a 17 mm round punch to cut a small disc of the quartz filter membrane. Place the disc in a 50 mL centrifuge tube, add 10 mL of high-purity water, and extract by ultrasonic oscillation for 30 min in an ultrasonic cleaner (KQ5200DE type, Kunshan Shumei). Filter the oscillated sample using a disposable needle filter (0.22 μm pore size, Tianjin Jinteng) to obtain the filtrate as the test solution for analysis.

[0040] (4) Turn on the chromatographic system, set the anion generator concentration to 20 mM, rinse the chromatographic column for 30 minutes, set the anion generator concentration to 2 mM, rinse the chromatographic column for 30 minutes, and use KOH solution for rinsing.

[0041] (5) The rinsing program of the anion self-regeneration inhibitor is set as follows: 0 min to 10 min, the rinsing solution concentration is 2 mM; 10 min to 24 min, the rinsing solution concentration increases from 2 mM to 30 mM; 24 min to 27 min, the rinsing solution concentration is maintained at 30 mM; 27 min to 35 min, the rinsing solution concentration decreases to 2 mM, and the rinsing solution is KOH solution.

[0042] (6) Prepare mixed standard solutions with seven concentration gradients, denoted as Mixed Standard Solution 1 to Mixed Standard Solution 7. The concentrations of FA, AA, MSA, GA, and SA in Mixed Standard Solution 1 to Mixed Standard Solution 7 are 0.01, 0.03, 0.05, 0.1, 0.3, 0.5, and 1 mg / L, respectively. - Cl - The concentrations of OA were 0.1 mg / L, 0.3, 0.5, 1, 3, 5, and 10 mg / L, respectively, and NO3... - SO4 2- The concentrations were 0.5, 1.5, 2.5, 5, 15, 25, and 50 mg / L, respectively, for PO4. 3- The concentrations were 0.2, 0.6, 1, 2, 6, 10, and 20 mg / L, respectively. In addition, separate standard solutions of each component were prepared using standard substances.

[0043] (7) Use a 1mL syringe to sequentially extract the standard solution from step (6), install the filter membrane, and inject it into the ion chromatograph for analysis and measurement. Determine the retention time of each component based on the elution results of the individual standard solutions. Determine the components corresponding to each peak in the mixed standard solution based on the elution times of each component in the mixed standard solution, and plot the standard curve based on the peak area and concentration.

[0044] (8) Use a 1mL syringe to sequentially draw the test solution from step (3), install the filter membrane, and inject it into the ion chromatograph for analysis and measurement to obtain the chromatogram, as shown below. Figure 1 As shown, according to Figure 1 As can be seen, the gradient elution procedure of this invention can achieve effective separation of multiple components with high separation degree. Based on the elution time of each component, the component corresponding to each peak in the test solution is identified; based on the standard curve quantification method, the concentration of each component in the test solution is obtained. (9) The pretreated blank filter membrane was subjected to extraction and ion chromatography under the same conditions to obtain the concentration of each component in the blank sample; then, according to Formula I, the true concentration of water-soluble organic acids and inorganic anions in the fine particulate matter was calculated: Formula I; In Formula I, C is the concentration of water-soluble components in the atmosphere, expressed in μg / m³. 3 C sample and C blank These represent the concentrations of the corresponding components in the leachate of the sample and blank filter membrane, respectively, in mg / L, and V is the sampling volume, in m³. 3 R is the area conversion factor (dimensionless), and in this embodiment, R is 4.737.

[0045] Recovery rate test: Formulated with FA, AA, MSA, OA, GA, SA, F - Cl - NO3 - SO4 2- and PO4 3- Solutions with concentrations of 0.3, 0.3, 0.3, 3, 0.3, 0.3, 3, 1.5, 7.5, 7.5, and 3 mg / L were tested under the conditions described in Example 1, and the test data for each component were obtained. The results are shown in Table 1. Table 1 Recovery rate test results

[0046] As can be seen from the data in Table 1, the detection method provided by this invention can detect samples of known concentrations with a recovery rate in the range of 92.35% to 106.48%, indicating high accuracy.

[0047] Comparative Example 1 All other conditions were the same as in Example 1, except that the elution program of the anion self-regeneration inhibitor was changed as follows: 0 min to 15 min, eluent concentration 2 mM; 15 min to 25 min, eluent concentration increased from 2 mM to 30 mM; 25 min to 28 min, eluent concentration maintained at 30 mM; 28 min to 35 min, eluent concentration decreased to 2 mM. The test solution from Example 1 was analyzed using the above elution program, and the resulting chromatogram is shown below. Figure 2 As shown, the results indicate that SA and PO4 are missing from the chromatogram under this elution program. 3- The peak.

[0048] Comparative Example 2 Other conditions were the same as in Example 1, except that the elution program of the anion self-regeneration inhibitor was changed as follows: 0 min to 10 min, eluent concentration 2 mM; 10 min to 24 min, eluent concentration increased from 2 mM to 20 mM; 24 min to 27 min, eluent concentration maintained at 20 mM; 27 min to 35 min, eluent concentration decreased to 2 mM. The test solution from Example 1 was analyzed using the above elution program, and the resulting chromatogram is shown below. Figure 3 As shown, the results indicate that SA and PO4 are lacking under this rinsing procedure. 3− The peak.

[0049] In summary, this invention provides a method for simultaneously measuring water-soluble organic acids and inorganic anions, particularly suitable for the simultaneous detection of water-soluble organic acids and inorganic anions in fine particulate matter. The method includes steps such as filter membrane pretreatment, particulate matter collection and preservation, sample extraction, column pretreatment and suppressor setting, standard solution calibration, sample injection, and chromatographic analysis. By designing a gradient elution program, organic acids and common inorganic anions can be effectively separated and simultaneously determined in the same chromatographic run. Based on standard curve quantification and combined with sampling volume conversion, the concentration of each target analyte in the atmosphere can be obtained. This invention significantly improves detection efficiency, avoids the shortcomings of traditional methods that require separate analysis of organic acids and inorganic anions, and has the advantages of simple operation, accurate measurement, and strong applicability.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for simultaneously measuring water-soluble organic acids and inorganic anions, characterized in that, Includes the following steps: The test solution was subjected to ion chromatography to obtain a chromatogram; qualitative and quantitative analysis was performed based on the chromatogram to obtain the types and concentrations of water-soluble organic acids and inorganic anions in the test solution; The water-soluble organic acids include formic acid, acetic acid, methanesulfonic acid, oxalic acid, succinic acid, and glutaric acid; the inorganic anions include F... - Cl - NO3 - SO4 2- and PO4 3- ; The eluent used in the ion chromatography detection is KOH solution, and the elution method is gradient elution. The elution program of the gradient elution is as follows: the eluent concentration is 1.5~2.5 mM from 0 min to 10 min, the eluent concentration increases from 1.5~2.5 mM to 29.5~30.5 mM from 10 min to 24 min, the eluent concentration is maintained at 29.5~30.5 mM from 24 min to 27 min, and the eluent concentration decreases to 1.5~2.5 mM from 27 min to 35 min.

2. The method according to claim 1, characterized in that, The test solution is a fine particulate matter extract, rainwater, or fog.

3. The method according to claim 2, characterized in that, The method for preparing the fine particulate matter extract is as follows: fine particulate matter is sampled using a filter membrane to obtain a sampling filter membrane; the sampling filter membrane is subjected to extraction treatment to obtain the fine particulate matter extract.

4. The method according to claim 3, characterized in that, The filter membrane is a quartz filter membrane; before sampling, the filter membrane is pretreated; the pretreatment includes heating the filter membrane at a temperature of 550°C for 5.5 hours; the sampling is performed using an atmospheric particulate matter sampler.

5. The method according to claim 3, characterized in that, The extraction agent used in the extraction process is deionized water; the extraction process is carried out under ultrasonic oscillation conditions, and the extraction time is 20-30 minutes.

6. The method according to claim 1, characterized in that, Before performing ion chromatography detection on the test solution, the chromatographic column is rinsed; the rinsing includes rinsing with a KOH solution of concentration of 29.5~30.5 mM for 25~35 min, and then rinsing with a KOH solution of concentration of 1.5~2.5 mM for 25~35 min.

7. The method according to claim 1, characterized in that, The qualitative analysis includes determining the types of water-soluble organic acids and inorganic anions in the test solution based on the retention times of the chromatographic peaks in the chromatogram.

8. The method according to claim 1, characterized in that, The quantification includes: determining the concentrations of water-soluble organic acids and inorganic anions in the test solution using a standard curve based on the height or area of ​​each chromatographic peak in the chromatogram; the standard curve is a curve showing the relationship between peak area or peak height and the concentration of the target component.

9. The method according to claim 8, characterized in that, The method for plotting the standard curve includes: preparing a series of mixed standard solutions using water-soluble organic acids and inorganic anionic standards, performing ion chromatography detection on the series of mixed standard solutions, and plotting the standard curve based on the detection results.

10. The method according to claim 2, characterized in that, When the test solution is a fine particulate matter extract, after obtaining the concentrations of water-soluble organic acids and inorganic anions in the test solution, the method further includes calculating the concentrations of water-soluble organic acids and inorganic anions in the atmosphere using Formula I. Equation I; In Equation I, C represents the concentration of the target component in the atmosphere, in μg / m³. 3 C sample and C blank These represent the concentrations of the corresponding components in the leachate of the sample and blank filter membrane, respectively, in mg / L, and V is the sampling volume, in m³. 3 R is the area conversion factor.

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