Method for determining chloride ions in ethylene glycol

Abstract

The invention discloses a method for determining chloride ions in ethylene glycol, which belongs to the technical field of detection, and is characterized by comprising the following steps: step 1, installing an ion capture column, an anion concentration column and a quantitative sample injector on an ion chromatograph; 2, preparing a regeneration solution; 3, preparing a carbonate mobile phase; 4, preparing ethylene glycol chloride ion series standard samples according to the chloride ion concentration in the ethylene glycol sample, and establishing a standard curve; and 5, diluting the sample solution and ultrapure water according to a mass ratio of 1: 1, analyzing by using an ion chromatograph, and quantifying through a standard curve. The method solves the problem that the matrix ethylene glycol directly enters an ion chromatographic column in the analysis process, chloride ion peaks are in normal distribution, meanwhile, the analysis repeatability is improved, and the method is mainly applied to determination of chloride ions in ethylene glycol.

Description

Technical Field

[0001] The invention relates to the field of chloride ion detection, and in particular to a method for determining chloride ions in ethylene glycol. Background Art

[0002] Ethylene glycol is a colorless, odorless, sweet, colorless, transparent, viscous liquid with low toxicity to animals. Ethylene glycol plays an important role in many fields. It can be used to make antifreeze, polyester, polyester, polyester resin, hygroscopic agent, plasticizer, surfactant, synthetic fiber, cosmetics, explosives, synthetic resin PET, etc. However, if the chloride ion content in the antifreeze is too high, it will corrode the equipment and cause leakage, which will undoubtedly greatly affect the service life of the equipment.

[0003] At present, the determination of chloride ions in ethylene glycol is mainly based on the analytical method in GB / T 14571.5-2016 "Test methods for industrial ethylene glycol Part 5: Determination of chloride ions by ion chromatography". However, in actual operation, this method has exposed some problems. During the analysis, the baseline of the ion chromatograph fluctuates greatly, the chloride ion peak is wide and severely tailed, and the repeatability is poor during continuous analysis. The existence of these problems has a great impact on the accuracy of the test results. Therefore, how to effectively solve the above problems and effectively improve the repeatability and accuracy of chloride ion analysis in ethylene glycol has become a top priority. This is not only related to the quality control of ethylene glycol products, but also to the stable operation and service life of related equipment.

[0004] To this end, our company established a special research team and after a long period of research, finally developed an analysis method for ethylene glycol chloride ions. This method is easy to operate and can accurately detect chloride ions in ethylene glycol. Summary of the invention

[0005] In order to solve the technical problems in the background technology, the main purpose of the present invention is to provide a method for determining chloride ions in ethylene glycol, and the technical scheme adopted is as follows:

[0006] A method for determining chloride ions in ethylene glycol, characterized in that:

[0007] Step 1: Prepare the test equipment;

[0008] The device comprises preparing test conditions: including ion chromatography mobile phase, suppressor regeneration liquid, mobile phase filter, double plunger high pressure reciprocating pump, quantitative control element, ultrapure water, detector, suppressor, ion chromatography column, automatic sample injector, six-way valve, peristaltic pump, anion capture column and chloride ion capture column;

[0009] The six-way valve has six pipeline interfaces, namely, a sample discharge port, a left connection port of a chloride ion capture column, a right connection port of a chloride ion capture column, a sample inlet, a mobile phase inlet, and a mobile phase outlet;

[0010] A waste liquid discharge port is provided on the left side of the quantitative control element, and an ion capture column is connected to the right side of the quantitative control element;

[0011] The suppressor is provided with an interface on each side;

[0012] The interfaces on the left are: regeneration liquid inlet, mobile phase inlet II and mobile phase outlet I;

[0013] The interfaces on the right are mobile phase inlet Ⅰ, mobile phase outlet Ⅱ and regeneration liquid outlet;

[0014] The mobile phase filter is connected to the ion chromatographic mobile phase;

[0015] The quantitative control element is connected to ultrapure water;

[0016] The suppressor regeneration liquid is connected to the suppressor regeneration liquid inlet;

[0017] The two ends of the ion chromatography column are respectively connected to the mobile phase outlet and the mobile phase inlet;

[0018] The automatic sample injector is connected to the sample inlet of the six-way valve;

[0019] The detector is a conductivity detector;

[0020] The ion chromatography column is an anion chromatography column, and the column stationary phase contains a resin or group with an anion exchange functional group;

[0021] The stationary phase of the anion capture column captures all anions;

[0022] The chloride ion capture column adsorbs and retains chloride ions in ethylene glycol;

[0023] The chloride ion capture column does not adsorb and retain ethylene glycol.

[0024] Step 2: Prepare sodium carbonate and sodium bicarbonate solution as ion chromatography mobile phase:

[0025] First, prepare 100-110g of sodium bicarbonate single substance solid; then weigh about 34g of sodium carbonate and about 8.5g of sodium bicarbonate and place them in a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and prepare a mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L; finally, use a pipette to transfer 10ml of the mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L to a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and shake well to obtain a mixed solution with a sodium carbonate concentration of about 3.2mmo l / L and sodium bicarbonate of about 1.0mmo l / L, which is placed in a 1000ml glass bottle to serve as an ion chromatography mobile phase;

[0026] Step 3: Prepare the suppressor regeneration solution

[0027] Pipette about 5 ml of high-purity concentrated sulfuric acid into a 1000 ml volumetric flask, dilute to 1000 ml with ultrapure water and shake well;

[0028] Step 4: When the ion chromatograph reaches the required configuration, use the mobile phase to balance the instrument. There are two instrument states: one is the state of the ion chromatograph absorbing samples, and the other is the state of separation and detection and instrument balance after the ion chromatograph injects samples. The following is a detailed description;

[0029] State 1: Ion chromatograph absorbs sample state

[0030] The mobile phase is extracted by a double-plunger high-pressure reciprocating pump, filtered by a mobile phase filter, and reaches the mobile phase inlet and mobile phase outlet of the six-way valve, passes through an ion chromatography column, reaches the mobile phase inlet Ⅰ of the suppressor, passes through the suppressor, reaches the mobile phase outlet Ⅰ of the suppressor, and then reaches the conductivity detector, and after being detected by the conductivity detector, continues to reach the suppressor inlet Ⅰ and suppressor outlet Ⅱ for waste liquid discharge;

[0031] The regeneration liquid is extracted by a peristaltic pump and discharged as waste liquid through the suppressor regeneration liquid inlet and suppressor regeneration liquid outlet;

[0032] The prepared sample is placed in the automatic sampler, and the quantitative control element extracts 200 μl of the sample through the sample inlet of the six-way valve, the right connection port of the chloride ion capture column, the left connection port of the chloride ion capture column and the sample discharge port. The ethylene glycol sample passes through the chloride ion capture column, and the chloride ions are adsorbed on the right side of the chloride ion capture column. The ethylene glycol flows into the middle pipeline connected to the anion capture column through the chloride ion capture column;

[0033] The second state: separation and detection after injection of ion chromatograph and instrument equilibrium state

[0034] After the instrument extracts 200 μl of sample through the first state operation, it starts to transfer the sample to the ion chromatography for separation and detection. The six-way valve performs the valve-cutting action. The mobile phase is extracted by the double-plunger high-pressure reciprocating pump, filtered through the mobile phase filter, reaches the mobile phase inlet of the six-way valve, the left connection port of the chloride ion capture column inlet, flows to the right connection port of the chloride ion capture column outlet and the mobile phase outlet. The sample flow direction is opposite to that when the sample is extracted in the first state. The chloride ions adsorbed on the chloride ion capture column are eluted and separated from the chloride ion capture column, and then enter the ion chromatography column, reach the mobile phase inlet I and mobile phase outlet I of the suppressor, and reach the conductivity detector for detection after passing through the suppressor. After passing through the detector, it continues to reach the mobile phase inlet II and mobile phase outlet II of the suppressor for waste liquid discharge.

[0035] The suppressor regeneration liquid is extracted by a peristaltic pump and discharged as waste liquid through the suppressor regeneration liquid inlet and suppressor regeneration liquid outlet;

[0036] The quantitative control element extracts ultrapure water through the anion capture column, then to the six-way valve, through the sample discharge port of the six-way valve, and then to the connected sample inlet port, and finally to the automatic sampler. At this time, the automatic sampler will set the transfer position through the ion chromatography method program, and discharge the ultrapure water of the cleaning pipeline discharged from the sample inlet port to the fixed waste liquid collection area for cleaning the sample injection line.

[0037] Step 5: Establishing the standard curve

[0038] Step 1: Preparation of chloride ion standard stock solution: Purchase chloride ion stock solution A with a standard solution concentration of 1000 mg / kg;

[0039] Step 2: Prepare a series of concentration standard solutions by diluting them according to the chloride ion content in the ethylene glycol sample:

[0040] Pipette 1 ml of 1000 mg / kg chloride ion stock solution A into a 100 ml volumetric flask, dilute to 100 ml with ultrapure water and shake well to obtain 10 mg / kg chloride ion stock solution B;

[0041] Pipette 1ml, 2ml, 5ml and 10ml of chloride ion stock solution B into a 100ml volumetric flask, dilute to 100ml with ultrapure water and shake well to obtain a series of standard solution groups C with concentrations of 0.1mg / kg, 0.2mg / kg, 0.5mg / kg and 1.0mg / kg respectively;

[0042] The series of standard solutions group C are placed on an automatic sampler for analysis, and are injected in order from low to high chloride ion concentrations, separated by a chromatographic column, and responded to on a conductivity detector to obtain the corresponding peak area;

[0043] A standard curve was established based on the concentration values ​​of standard solution group C and the corresponding peak areas to obtain a linear equation. The linear coefficient should be greater than 0.999.

[0044] Step 6: Measure 6-8g of the sample to be analyzed into a clean glass test tube with a stopper, add the same amount of ultrapure water, cover the stopper and shake thoroughly;

[0045] Step 7: Filter the sample shaken in step 6 with a water filter membrane, discard the first 3 ml of filtrate, and collect the middle 10 ml of filtrate with a plastic centrifuge tube;

[0046] Step 8: Place the centrifuge tube containing the filtrate in step 7 on an automatic sampler for analysis to obtain the peak area of ​​the chloride ion response in the sample, and calculate the chloride ion content in the sample through the standard curve.

[0047] Furthermore, the chloride ion concentration in all ultrapure water used for dilution is less than 0.02 mg / kg.

[0048] The present invention has the following beneficial effects:

[0049] After the instrument is modified, a chloride ion preconcentrator column and a metering element for controlling the injection volume are used simultaneously. The function of the quantitative element is to completely replace the quantitative loop to accurately quantify a specific injection volume of ethylene glycol sample; the function of the chloride ion preconcentrator column is that when the quantitative element extracts a specific amount of ethylene glycol sample through the chloride ion preconcentrator column on the six-way valve, all chloride ions in the ethylene glycol sample are adsorbed on the chloride ion preconcentrator column, while ethylene glycol will not be adsorbed and discharged out of the system through the six-way valve, thereby ensuring that ethylene glycol will not enter the chromatographic column when the valve is cut for injection. This can reduce the impact of ethylene glycol on the life of the chromatographic column, and greatly reduce the baseline noise and baseline drift affected by ethylene glycol, so that a good positive distribution peak shape can be obtained.

[0050] The instrument uses an ion capture column to adsorb and capture chloride ions in ultrapure water, reducing the deviation of the analysis results caused by chloride ions in ultrapure water.

[0051] The sample pretreatment was performed by diluting the ethylene glycol sample with ultrapure water in a mass ratio of 1:1. The viscosity of the diluted ethylene glycol sample was reduced, and the repeatability of the injection volume was improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The device configured for steps 1 to 4 of the present invention is also the second state diagram in step 4;

[0053] Figure 2 A graph obtained by analyzing the instrument configured for the present invention;

[0054] Figure 3 The chromatogram is obtained by analyzing the instrument configured by the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0056] A method for determining chloride ions in ethylene glycol, characterized in that:

[0057] Step 1: Prepare the test equipment;

[0058] The device comprises preparing test conditions: including ion chromatography mobile phase 1, suppressor regeneration liquid 2, mobile phase filter 3, double plunger high pressure reciprocating pump 4, quantitative control element 5, ultrapure water 6, detector 7, suppressor 8, ion chromatography column 9, automatic sample injector 10, six-way valve 11, peristaltic pump 27, anion capture column 12 and chloride ion capture column 18;

[0059] The six-way valve 11 has six pipeline interfaces, namely, a sample discharge port 14, a chloride ion capture column left connection port 13, a chloride ion capture column right connection port 16, a sample inlet port 15, a mobile phase inlet port 19 and a mobile phase outlet port 17;

[0060] The left side of the quantitative control element 5 is provided with a waste liquid discharge port 20, and the right side of the quantitative control element 5 is connected to an ion capture column 12;

[0061] The suppressor 8 is provided with three interfaces on both sides respectively;

[0062] The three interfaces on the left are: regeneration liquid inlet 23, mobile phase inlet II 21 and mobile phase outlet I 26;

[0063] The three interfaces on the right are mobile phase inlet Ⅰ 25, mobile phase outlet Ⅱ 22 and regeneration liquid outlet 24;

[0064] The mobile phase filter 3 is connected to the ion chromatography mobile phase 1;

[0065] The quantitative control element 5 is connected to ultrapure water 6;

[0066] The suppressor regeneration liquid 2 is connected to the regeneration liquid inlet 23 of the suppressor 8;

[0067] The two ends of the ion chromatography column 9 are connected to the mobile phase outlet 17 and the mobile phase inlet 25 respectively;

[0068] The automatic sample injector 10 is connected to the sample inlet of the six-way valve 11 and the cleaning pipeline discharge port 15;

[0069] The detector 7 is a conductivity detector;

[0070] The ion chromatography column 9 is an anion chromatography column, and the column stationary phase contains a resin or group with anion exchange functional groups;

[0071] The stationary phase of the anion capture column 12 captures all anions;

[0072] The chloride ion capture column 18 adsorbs and retains chloride ions in ethylene glycol;

[0073] The chloride ion capture column 18 does not adsorb and retain ethylene glycol;

[0074] Step 2: prepare sodium carbonate and sodium bicarbonate solution as ion chromatography mobile phase;

[0075] First, prepare 100-110g of sodium bicarbonate single substance solid; then weigh 34g of sodium carbonate and about 8.5g of sodium bicarbonate and place them in a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and prepare a mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L; finally, use a pipette to transfer 10ml of the mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L to a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and shake well to obtain a mixed solution with a sodium carbonate concentration of 3.2mmol / L and sodium bicarbonate of about 1.0mmol / L, which is placed in a 1000ml glass bottle to serve as an ion chromatography mobile phase;

[0076] Step 3: Prepare suppressor regeneration solution;

[0077] Pipette about 5 ml of high-purity concentrated sulfuric acid into a 1000 ml volumetric flask, dilute to 1000 ml with ultrapure water and shake well;

[0078] Step 4: Establishment of standard curve;

[0079] Step 1: Preparation of chloride ion standard stock solution: This article purchases 1000 mg / kg chloride ion stock solution A for use;

[0080] Step 2: Prepare a series of concentration standard solutions by diluting them according to the chloride ion content in the ethylene glycol sample:

[0081] Pipette 1 ml of 1000 mg / kg chloride ion stock solution A into a 100 ml volumetric flask and dilute to volume with ultrapure water to obtain 10 mg / kg chloride ion stock solution B;

[0082] Pipette 1 ml, 2 ml, 5 ml, and 10 ml of chloride ion stock solution B into a 100 ml volumetric flask, and dilute to volume with ultrapure water to obtain a series of standard solution groups C with concentrations of 0.1 mg / kg, 0.2 mg / kg, 0.5 mg / kg, and 1.0 mg / kg, respectively;

[0083] Step 3: Place the series concentration standard solution group C on the automatic sampler for analysis, and inject the samples in order from low to high chloride ion concentrations, separate them through the chromatographic column, respond on the conductivity detector, and obtain the corresponding peak area;

[0084] Step 4: Establish a standard curve based on the standard solutions of different concentrations in standard solution group C and the corresponding peak areas to obtain a linear equation with a linear coefficient greater than 0.999. Figure 2 For example.

[0085] Step 5: Measure 6-8g of the sample to be analyzed into a clean glass test tube with a stopper, add the same amount of ultrapure water, cover the stopper and shake thoroughly;

[0086] Step 6: Filter the sample shaken in step 5 with a water filter membrane, discard the first 3 ml of filtrate, and collect the middle 10 ml of filtrate with a plastic centrifuge tube;

[0087] Step 7: Place the plastic centrifuge tube containing the filtrate in step 6 on an automatic sampler for analysis, obtain the peak area of ​​the chloride ion in the sample in the conductivity detector, and calculate the chloride ion content in the sample through the standard curve;

[0088] Step 8: Place the centrifuge tube containing the filtrate in step 7 on the automatic sampler for analysis to obtain the peak area of ​​the chloride ion response in the sample, and calculate the chloride ion content in the sample through the standard curve.

[0089] Furthermore, the chloride ion concentration in all ultrapure water used for dilution was less than 0.02 mg / kg;

[0090] 500 ml of 0.41 mg / kg ethylene glycol quality control sample E and 10 mg / kg chloride ion stock solution F were selected and analyzed using the instrument configuration of GB / T 14571.5-2016 and the instrument configuration of this patent respectively.

[0091] The following examples are used to illustrate:

[0092] Example 1

[0093] Sample preparation: Sample ①

[0094] Select quality control sample E

[0095] Sample chloride ion determination:

[0096] Take three 25ml plastic test tubes and put 15g of sample ① into each tube. Measure sample ① and find out the chloride ion content from the calibration curve drawn in advance.

[0097] Example 2

[0098] Sample preparation: Sample ②

[0099] Prepare a 100 ml glass colorimetric tube with a stopper, add 30 g of quality control sample E and ultrapure water into it respectively, cover the stopper and shake thoroughly to dilute the sample 1:1.

[0100] Sample chloride ion determination:

[0101] Take three 25ml plastic test tubes and put 15g of sample ② into each tube. Measure sample ② and find out the chloride ion content from the calibration curve drawn in advance.

[0102] Example 3

[0103] Sample preparation: Sample ③

[0104] Prepare a 250ml glass colorimetric tube with a stopper, accurately weigh and add 100g of quality control sample E and 5g of chloride ion stock solution F, cover the stopper and shake thoroughly.

[0105] Sample chloride ion determination:

[0106] Take three 25ml plastic test tubes, accurately weigh and put 15g of sample ③ into each tube, measure sample ③, and find out the chloride ion content from the calibration curve drawn in advance.

[0107] Example 4

[0108] Sample preparation: Sample ④

[0109] Prepare a 250ml stoppered glass colorimetric tube, accurately weigh and add 100g of quality control sample E and 5g of chloride ion stock solution F, cover the stopper and shake thoroughly. Then take 30g of the shaken sample and add it to a 100ml stoppered glass colorimetric tube, add 30g of water, cover the stopper and shake thoroughly to dilute the sample 1:1.

[0110] Sample chloride ion determination:

[0111] Take three 25ml plastic test tubes and put 15g of sample ④ into each tube. Measure sample ④ and find out the chloride ion content from the calibration curve drawn in advance.

[0112] Example 5

[0113] Sample preparation: Sample ⑤

[0114] Select quality control sample E

[0115] Sample chloride ion determination:

[0116] Take three 25ml plastic test tubes and put 15g of sample ⑤ into each tube. Measure sample ⑤ and find out the chloride ion content from the calibration curve drawn in advance.

[0117] Example 6

[0118] Sample preparation: Sample ⑥

[0119] Prepare a 100 ml glass colorimetric tube with a stopper, add 30 g of quality control sample E and ultrapure water into it respectively, cover the stopper and shake thoroughly to dilute the sample 1:1.

[0120] Sample chloride ion determination:

[0121] Take three 25 ml plastic test tubes, put 15 g of sample ⑥ into each tube, measure sample ⑥, and find out the chloride ion content from the calibration curve drawn in advance.

[0122] Example 7

[0123] Sample preparation: Sample ⑦

[0124] Prepare a 250ml glass colorimetric tube with a stopper, accurately weigh and add 100g of quality control sample E and 5g of chloride ion stock solution F, cover the stopper and shake thoroughly.

[0125] Sample chloride ion determination:

[0126] Take three 25ml plastic test tubes, accurately weigh and put 15g of sample ⑦ into each tube, measure sample ⑦, and find out the chloride ion content from the calibration curve drawn in advance.

[0127] Example 8

[0128] Sample preparation: Sample ⑧

[0129] Prepare a 250ml stoppered glass colorimetric tube, accurately weigh and add 100g of quality control sample E and 5g of chloride ion stock solution F, cover the stopper and shake thoroughly. Then take 30g of the shaken sample and add it to a 100ml stoppered glass colorimetric tube, add 30g of water, cover the stopper and shake thoroughly to dilute the sample 1:1.

[0130] Sample chloride ion determination:

[0131] Take three 25 ml plastic test tubes and put 15 g of sample ⑧ into each tube. Measure sample ⑧ and find out the chloride ion content from the calibration curve drawn in advance.

[0132] Note: Examples 1 to 4 were analyzed using the instrument configuration of GB / T 14571.5-2016, and Examples 5 to 8 were analyzed using the instrument configuration of this patent.

[0133] Chloride ion in ethylene glycol was determined according to Examples 1 to 8, and the analysis results are shown in the following table:

[0134]

[0135] The above results show that:

[0136] aThrough Example 1 and Example 2, it is found that the accuracy and repeatability of Example 2 are higher than those of Example 1, but both results meet the repeatability error. That is, after the sample is diluted with ultrapure water, the viscosity of the sample is reduced, which is more conducive to the repeatability and accuracy of the analysis results.

[0137] b It was found through Example 3 and Example 4 that the analysis directly after the ethylene glycol stock solution was spiked had poor repeatability and low recovery rate than the analysis after 1:1 dilution with ultrapure water, which did not meet the requirements.

[0138] c Through Example 5 and Example 6, it was found that when the instrument configured by the present patent analyzes samples, the analysis repeatability and accuracy are improved when the samples are diluted or not, and meet the requirements, but the accuracy is higher when the samples are diluted.

[0139] d Through Example 7 and Example 8, it was found that when the quality control sample was analyzed after being spiked, the repeatability and accuracy were improved when analyzed using the instrument configured by this patent, but the recovery rate of the diluted sample was slightly higher than that of the undiluted sample.

[0140] Finally, it should be noted that the embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the implementation methods of the present invention.

[0141] The ethylene glycol chloride ion analysis method of the present invention reduces the influence of ethylene glycol viscosity on the injection amount, the influence of ethylene glycol matrix on the separation of chromatographic columns and the influence of ethylene glycol on the response of conductivity detectors through unique instrument configuration and sample pretreatment methods, thereby improving the repeatability and accuracy of the analysis results. The sample pretreatment process is simple to operate and is suitable for promotion and application.

Claims

1. A method for determining chloride ions in ethylene glycol, characterized in that: Step 1: Prepare the test equipment; The device comprises preparation test conditions: including ion chromatography mobile phase (1), suppressor regeneration liquid (2), mobile phase filter (3), double plunger high pressure reciprocating pump (4), quantitative control element (5), ultrapure water (6), detector (7), suppressor (8), ion chromatography column (9), automatic sample injector (10), six-way valve (11), peristaltic pump (27), anion capture column (12) and chloride ion capture column (18); The six-way valve (11) has six pipeline interfaces, namely a sample discharge port (14), a left connection port (13) of a chloride ion capture column, a right connection port (16) of a chloride ion capture column, a sample inlet port (15), a mobile phase inlet port (19) and a mobile phase outlet port (17); The left side of the quantitative control element (5) is provided with a waste liquid discharge port (20), and the right side of the quantitative control element (5) is connected to an ion capture column (12); The suppressor (8) is provided with three interfaces on both sides respectively; The three interfaces on the left are: regeneration liquid inlet (23), mobile phase inlet II (21) and mobile phase outlet I (26); The three interfaces on the right are mobile phase inlet I (25), mobile phase outlet II (22) and regeneration liquid outlet (24); The mobile phase filter (3) is connected to the ion chromatography mobile phase (1); The quantitative control element (5) is connected to ultrapure water (6); The suppressor regeneration liquid (2) is connected to the regeneration liquid inlet (23) of the suppressor (8); The two ends of the ion chromatography column (9) are respectively connected to a mobile phase outlet (17) and a mobile phase inlet (25); The automatic sample injector (10) is connected to the sample inlet of the six-way valve (11) and the cleaning pipeline discharge port (15); The detector (7) is a conductivity detector; The ion chromatography column (9) is an anion chromatography column, and the column stationary phase contains a resin or group with anion exchange functional groups; The stationary phase of the anion capture column (12) captures all anions; The chloride ion capture column (18) adsorbs and retains chloride ions in ethylene glycol; The chloride ion capture column (18) does not adsorb and retain ethylene glycol; Step 2: prepare sodium carbonate and sodium bicarbonate solution as ion chromatography mobile phase; First, prepare 100-110g of sodium bicarbonate solid; then weigh 34g of sodium carbonate and about 8.5g of sodium bicarbonate and place them in a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and prepare a mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L; finally, use a pipette to transfer 10ml of the mobile phase mother solution with a sodium carbonate concentration of about 0.32mol / L and sodium bicarbonate of about 0.1mol / L to a 1000ml volumetric flask, dilute to 1000ml with ultrapure water, and shake well to obtain a mixed solution with a sodium carbonate concentration of 3.2mmol / L and sodium bicarbonate of about 1.0mmol / L, which is placed in a 1000ml glass bottle to serve as an ion chromatography mobile phase; Step 3: Prepare 0.4%-0.6% sulfuric acid solution as the suppressor regeneration solution; Step 4: Prepare a series of chloride ion standard solutions to establish an ion chromatographic curve. Determine the concentration of the standard solution based on the chloride ion content in the ethylene glycol sample and prepare chloride ion standard solutions of different concentrations. Step 5: Establishing a standard curve, analyzing the chloride ion standard solutions prepared in step 4 on an ion chromatograph in sequence, obtaining the response values ​​of chloride ions respectively, and establishing a linear standard curve according to the response values ​​of different chloride ion standard solutions on the detector; Step 6: Ethylene glycol sample analysis First, sample pretreatment is performed: the sample to be analyzed is injected into a centrifuge tube, ultrapure water is added to mix thoroughly, and then filtered using a filter membrane; The filtered sample is then placed on an ion chromatograph for analysis, and the chloride ion result is calculated using a standard curve; Step 6: Measure 6-8g of the sample to be analyzed into a clean glass test tube with a stopper, add the same amount of ultrapure water, cover the stopper and shake thoroughly; Step 7: Filter the sample shaken in step 6 with a water filter membrane, discard the first 3 ml of filtrate, and collect the middle 10 ml of filtrate with a plastic centrifuge tube; Step 8: Place the centrifuge tube containing the filtrate in step 7 on an automatic sampler for analysis to obtain the peak area of ​​the chloride ion response in the sample, and calculate the chloride ion content in the sample through the standard curve.

2. The method according to claim 1, wherein: The quantitative control element in step 1 determines the injection volume, and the sample injection volume is set to 200ul.

3. The method according to claim 1, wherein: Use a vacuum pump to filter the prepared mobile phase through a water filter membrane.

4. The method according to claim 1, wherein: The curve equation in step 5 has a curve equation coefficient greater than 0.

999.

5. The method for determining chloride ions in ethylene glycol according to claim 1, wherein: The chloride ion content in ultrapure water does not exceed 0.02 mg / kg.

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