Method for determining halogen content in electrolyte by oxygen bomb combustion-turbidimetry

Abstract

The invention provides a method for determining halogen content in electrolyte by oxygen bomb combustion-turbidimetry. According to the method, the halogen in the electrolyte with complex components and extremely low halogen content is converted by using an oxygen bomb combustion method, and the converted halogen acid is absorbed and extracted by using the absorption liquid with specific composition, so that the detection sensitivity of the halogen content is remarkably improved, and the detection limit of the halogen in the electrolyte can be as low as 0.20 PPM. According to the method, the oxygen bomb combustion-turbidimetry is applied to detection of trace halogen in the aluminum electrolytic capacitor electrolyte for the first time, the detection accuracy is improved by optimizing the composition of the absorption liquid and the sampling proportion of the absorption liquid and the electrolyte, the influence of phosphate and chromaticity on halogen detection by the turbidimetry is avoided, and the detection accuracy is improved. The method has the advantages of economy, convenience, high efficiency, stability, good detection accuracy and the like.

Description

Technical Field

[0001] The invention relates to the field of detection technology, in particular to a method for determining the halogen content in an electrolyte by using an oxygen bomb combustion-turbidimetry method. Background Art

[0002] In the manufacturing process of electronic components, impurity ions such as chloride ions will corrode the anode and cause fatal damage to electronic components, so the chlorine content of raw materials must be tested. The chlorine content of raw materials is generally controlled below 1PPM (1000ug / kg), and the chloride ions of aluminum foil, electrolyte, electrolytic paper, and chemical materials are generally strictly controlled. The main solvents of capacitor electrolytes are ethylene glycol, γ-butyrolactone, NN dimethylformamide, water, etc., and the solvent accounts for 70%-90%; the solute is mainly composed of organic matter and its salts, inorganic salts, etc., accounting for 10%-30%. Since the electrolyte is mainly an organic mixture, it has high chroma, high viscosity, and contains a variety of interfering substances, which greatly interferes with the determination of impurity ions such as chlorine, so the electrolyte must be pretreated. At present, the main methods for detecting the chlorine content of electrolytes in the industry are direct dilution turbidimetry and ion chromatography. This method dilutes the electrolyte and directly injects it for testing. The test results are inaccurate due to the interference of the complex components of the electrolyte; another method is to directly dilute the electrolyte in acidic water or an aqueous solution of alcohol, and add silver nitrate for turbidimetry testing. This method does not exclude the influence of color, and the use of a spectrophotometer will increase the absorbance. It can only test inorganic chloride ions, and organic chlorine cannot be detected. Electrolytes generally contain phosphates, which form dark substances and precipitations with silver nitrate in organic systems. The turbidity of silver chloride cannot be accurately measured because silver nitrate is oxidizing and turns gray-black when it encounters organic matter in the electrolyte. The electrolyte also contains a large amount of ammonium ions. In the non-aqueous potentiometric titration method, ammonium ions and phosphates will seriously affect the test results, and the pretreatment process is troublesome, so the non-aqueous potentiometric titration method is not suitable for the determination of chloride ions in these electrolytes.

[0003] Another common pre-treatment method for detecting electrolyte impurity ions in the industry is high-temperature ashing. That is, the electrolyte is first burned to volatilize the solvent, and then placed in a high-temperature box furnace for high-temperature ashing, generally at 500-700°C, and the ash is dissolved in water for testing. However, this method will cause chlorine loss during high-temperature oxidation, resulting in a serious low chlorine content in the tested electrolyte, and it is also time-consuming and energy-consuming. Although the addition of an ashing agent will inhibit the loss of certain elements to a certain extent, the chlorine content in the electrolyte is generally low, and it is difficult to inhibit the loss of chlorine by auxiliary ashing agents. The chloride ion content of electrolytic paper also seriously affects the life of aluminum electrolytic capacitors. At present, the chloride ion concentration in electrolytic paper is mainly tested by extraction or ultrasonic vibration to dissolve the chloride ions in the electrolytic paper into water, and then tested by ion chromatography. This method can only test the inorganic chloride ions on the surface of the electrolytic paper, and it is difficult to completely extract the halogens in the sample by the extraction method.

[0004] Therefore, it is necessary to provide a detection process for halogen in raw materials of aluminum electrolytic capacitors with high detection accuracy. Summary of the invention

[0005] The purpose of the present invention is to overcome the above existing technical problems and provide a detection process for the halogen content in electrolytes with high detection accuracy. The present invention collects the halogen in the sample to be tested by oxygen bomb combustion method, and then uses turbidimetry to quantitatively test the halogen content.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry comprises the following steps:

[0008] After the S1 electrolyte is dehydrated, it is added to an oxygen bomb device with an absorbing liquid, mixed evenly, sealed, and oxygen is introduced to burn in a pure oxygen environment;

[0009] After the combustion is completed, the mixture is cooled to below 25°C, the gas in the oxygen bomb device is discharged, and the halide in the gas is dissolved in the absorption liquid. The absorption liquid after combustion is combined with the eluent used to elute the inside of the oxygen bomb device, and the filtrate after filtration is used as the sample to be tested;

[0010] Wherein, the absorption liquid contains carbonate, bicarbonate and alkali solution;

[0011] The electrolyte includes at least one of an electrolyte solution and a solid electrolyte;

[0012] The mass volume ratio of the electrolyte to the absorption liquid is 1g:(5-50)mL;

[0013] S2 uses a turbidity method to test the halogen content in the sample obtained in step S1.

[0014] After the electrolyte / electrolytic paper is burned in an oxygen bomb, halogen elements such as chlorine and bromine are converted into corresponding hydrochloric acid and hydrobromic acid gases, which can be fully absorbed by the alkali solution after cooling; the inventors of the present invention have also found that adding carbonates and bicarbonates to the alkali solution at the same time can also work together with the substances in the combustion products of the electrolyte to significantly improve the absorption performance of halogens, as well as the sensitivity and stability of color during the turbidity test process, and can test trace halogens in the electrolyte.

[0015] Preferably, the absorption liquid comprises the following raw materials: 1-100 mmol / L alkaline solution, 1-50 mmol / L carbonate solution, and 1-50 mmol / L bicarbonate solution.

[0016] Preferably, the carbonate includes at least one of sodium carbonate and potassium carbonate.

[0017] Preferably, in the absorption liquid, the bicarbonate includes at least one of sodium bicarbonate and potassium bicarbonate.

[0018] Preferably, the alkali includes at least one of sodium hydroxide and potassium hydroxide.

[0019] Preferably, a combustion improver is further added to the oxygen bomb device, and the combustion improver includes at least one of isooctane, anhydrous ethanol, and benzoic acid. The combustion improver is added to the oxygen bomb combustion device.

[0020] Preferably, in the S1 process, 0.5 g of combustion-supporting agent benzoic acid tablets are placed in a combustion cup, and 1-5 mL of anhydrous ethanol is added dropwise; the combustion-supporting agent is fully in contact with the electrolyte sample, which is more conducive to complete combustion of the electrolyte.

[0021] Preferably, the sampling weight ratio of the electrolyte to the standard chloride ion solution is 1:1.

[0022] Within this ratio range, it is conducive to the complete combustion of the electrolyte or solid electrolyte and the absorption of the hydrohalic acid.

[0023] Preferably, the electrolyte contains 10-30 wt % of solute and 40%-90% of solvent.

[0024] The solvent includes at least one of water, ethylene glycol, γ-butyrolactone, N,N-dimethylformamide, carbonate, dimethyl carbonate, polycarbonate, acetone, methyl formate, ethyl acetate, pyridine, ether, and ethylene carbonate.

[0025] The solutes include but are not limited to:

[0026] 1) At least one of organic carboxylic acids and salts thereof, boric acid and salts thereof, and amino acids and salts thereof. The organic carboxylic acids and salts thereof include at least one of ammonium formate, ammonium benzoate, ammonium citrate, ammonium adipate, ammonium succinate, ammonium maleate, ammonium phthalate, quaternary ammonium salts, ammonium sebacate, ammonium azelate, ammonium benzoate, butyl ammonium suberate, tetramethylammonium maleate, tetraethylammonium maleate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and dodecanedionate; the boric acid and salts thereof include but are not limited to at least one of boric acid and ammonium pentaborate.

[0027] 2) Organic amine additives: for example, including but not limited to at least one of triethylamine, triethanolamine, tributylamine, ethylenediamine, hexamethylenediamine, propylamine, formamide, and acetamide;

[0028] 3) Functional additives: including but not limited to phosphoric acid and its salts, phosphorous acid and its salts; specifically including but not limited to at least one of phosphoric acid, ammonium phosphate, hypophosphorous acid, and ammonium hypophosphite;

[0029] 4) Interface stabilizers include but are not limited to aromatic nitro compounds, aminocarboxylic acids, citric acid, hydroxy aromatic compounds, etc.

[0030] The electrolyte selected by the present invention contains yellow substances such as organic amines, organic carboxylic acids, and aromatic nitro compounds. If the turbidimetric method is used for testing directly without pretreatment, the color will affect the test results of the sample to be tested. After the electrolyte is burned in an oxygen bomb combustion device, the above-mentioned colored substances will undergo complex chemical reactions and decompose, and the sample to be tested will become colorless, which is conducive to using the turbidimetric method to test the halogen content in the sample. Preferably, the solid electrolyte includes at least one of electrolytic paper, polypyrrole, polythiophene, and polyaniline; the electrolytic paper includes plant fibers, and the plant fibers include but are not limited to at least one of cellulose, pentosan, and lignin.

[0031] Preferably, in step S1, oxygen is introduced into the oxygen bomb device to a pressure of 1-5 MPa.

[0032] Preferably, the reagent used for rinsing the oxygen bomb device is an absorption liquid.

[0033] Preferably, the turbidimetric test method comprises the following steps:

[0034] (1) preparing a series of 0-50 PPM halogen ion standard solutions using water-soluble salts containing corresponding halogens; concentrating and fixing the eluent obtained in step S1 to obtain a test solution;

[0035] (2) Add nitric acid solution to the above-mentioned halogen ion standard solution and the test solution and shake well; then add silver nitrate solution and shake well; after standing for 15 minutes, test the turbidity with a spectrophotometer and test the absorbance at a wavelength of 450-500 nm; obtain a linear curve with the concentration of the halogen ion standard solution as the X-axis and the absorbance as the Y-axis; then substitute the absorbance of the test solution into the relationship obtained by linear curve fitting to calculate the halogen content in the electrolyte.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention uses an oxygen bomb combustion method to convert the halogen in an electrolyte with complex components and extremely low halogen content, and uses an absorption liquid with a specific composition to absorb and extract the converted hydrohalic acid, thereby significantly improving the detection sensitivity of the turbidimetric method for testing the halogen content, and the detection limit of the halogen in the electrolyte can be as low as 0.20 PPM.

[0038] The present invention applies oxygen bomb combustion-turbidimetry to the detection of trace halogens in the electrolyte of aluminum electrolytic capacitors for the first time, and tests the overall halogen content of the electrolyte. By optimizing the composition of the absorption liquid and the sampling ratio of the absorption liquid and the electrolyte, the detection accuracy is improved, and the influence of phosphate and colorimetry on the turbidimetric detection of halogens is avoided. The invention has the advantages of being economical, convenient, efficient, stable and having good detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 In Example 1 of the present invention, the standard turbidity curve is prepared using the absorbance of chloride ion standard solutions of different concentrations.

[0040] Figure 2 FIG. 1 is a schematic diagram of oxygen bomb combustion according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] For better explanation of the purpose, technical scheme and advantage of the present invention, the present invention will be further described below in conjunction with specific embodiment and accompanying drawing, but embodiment does not limit the present invention in any form.Unless otherwise specified, the reagent, method and equipment adopted in the present invention are conventional reagents, methods and equipment in the art.Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

[0042] Example 1

[0043] This embodiment provides a method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry, comprising the following steps:

[0044] (1) Weighing of electrolyte: Take 5.0 g of each of electrolytes 1#, 2#, and 3#, wherein electrolytes 1#, 2#, 3#, and 4# are halogen-free electrolytes, electrolytes with a chloride ion content of 5 PPM, electrolytes with a chloride ion content of 10 PPM, and electrolytes with a chloride ion content of 50 PPM, respectively. Among them, electrolytes 2#, 3#, and 4# are obtained by adding sodium chloride and further diluting (sodium chloride comes from the Aladdin brand and is used after being ashed at 500°C); after weighing, the electrolytes need to be placed in an oven to evaporate moisture for 2 hours (moisture content ≤ 2.5%, which is conducive to ignition and combustion in an oxygen bomb. If the moisture content is too high, it is easy to cause difficulty in ignition or even failure to ignite) for use;

[0045] Table 1 Composition of the electrolyte to be tested

[0046]

[0047] (2) Preparation of absorption liquid:

[0048] Take the following solutions and mix them as the absorption liquid: 10mL of 20mmol / L KOH, 10mL of 20mmol / L sodium carbonate and 10mL of 20mmol / L sodium bicarbonate to obtain the absorption liquid. Take 10mL of the absorption liquid at the bottom of the oxygen bomb, take 20mL and put it in the absorption test tube, and connect the absorption test tube to the exhaust port of the oxygen bomb combustion device. Make the ratio of the mass of the electrolyte to be tested to the volume of the absorption liquid 5g:30mL;

[0049] (3) 5.0 g of the electrolyte dried in step (1) and 0.5 g of a combustion-supporting agent, benzoic acid tablets, are placed in a combustion cup, a combustion wire is connected, and 2.0 mL of anhydrous ethanol is added dropwise; the combustion wire is fully in contact with the electrolyte sample; the oxygen bomb device is tightened, and oxygen is slowly injected into the oxygen bomb, and oxygen is repeatedly filled to 5 MPa. After the oxygen filling is completed, the air is vented and then oxygenated again. This is repeated 3 times, and the air in the oxygen bomb container can be removed to reach a pure oxygen environment, which is easy to burn;

[0050] (4) Electrolyte combustion:

[0051] Use the electronic igniter to ignite the flame. Wait until the indicator light goes out.

[0052] (5) Collecting the eluent:

[0053] After the indicator light goes out, release the air pressure at a slow and uniform rate so that only small bubbles can be observed slowly emerging in the absorption test tube, so that the halogen-containing gas after combustion in the oxygen bomb is fully absorbed. After the pressure is completely discharged, place the burner in cold water to cool. After cooling, open the oxygen bomb, pour out the absorption liquid in the oxygen bomb, and then use the absorption liquid in the absorption test tube to rinse the inner wall and combustion cup of the oxygen bomb device. Finally, rinse the inner wall and combustion cup of the oxygen bomb device with a small amount of ultrapure water, and collect all the absorption liquid and the eluent; the eluent and the absorption liquid are mixed and placed in a beaker for ultrasonic vibration for 5 to 10 minutes, and then filtered with a 0.45μm filter membrane, and the filtrate is placed in a constant temperature water area (85℃) to evaporate excess water until the remaining volume of the filtrate is less than 25mL. Take all the filtrate and finally put it in a colorimetric tube, and make up to 25mL with ultrapure water. This solution is the test solution; see the structural diagram for details. Figure 2 ;

[0054] (6) Preparation of chloride ion standard solution:

[0055] Weigh 1.6490 g of pretreated sodium chloride, dissolve it in a small amount of ultrapure water, dilute to 1000 mL, and obtain 1000 PPM chloride ion standard solution. Then dilute the 1000 PPM standard solution to obtain chloride ion standard solutions of different concentrations (1-50 PPM); take 5 mL of chloride ion standard solutions with concentrations of 0 PPM-50 PPM in colorimetric tubes, and dilute to 25 mL with ultrapure water;

[0056] (7) Testing:

[0057] Add 2mL of 4mol / L nitric acid solution to the colorimetric tubes of the above-mentioned chloride ion standard solutions and the test solution, and shake well; then add 2mL of 0.100mol / L silver nitrate solution, and shake well; let it stand for 10 minutes, and test the absorbance at a wavelength of 458nm with 0PPM of the test solution as a blank comparison, and complete the test within 20 minutes;

[0058] (8) Calculation of halogen content in electrolyte:

[0059] First, prepare the standard chloride ion turbidity curve: use the linear relationship to calculate the chloride ion content in the eluent; obtain the absorbance of each standard chloride ion turbid solution, and draw the standard curve as shown in the figure. Figure 1 As shown in the figure, the standard curve can be obtained as y=0.0068x-0.0005, and the correlation is 0.9985;

[0060] Calculation of halogen content: Substitute the absorbance of electrolytes 1#-4# measured in step (7) into the standard curve of standard chloride ion turbid solution to calculate the halogen content in the electrolyte. The specific test results are shown in Table 2:

[0061] In Table 2, the halogen content in the test liquid is the result of taking the average value after 5 repeated tests on the same test sample, and the standard deviation also refers to the standard deviation of these 5 test results. It can be seen that the standard deviation is <0.5;

[0062] The test result accuracy (%) is calculated according to the following formula:

[0063] Accuracy (%) = 1-|CC 0 ∣ / C 0 *100%.

[0064] Table 2

[0065]

[0066] Example 2

[0067] The present embodiment provides a method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry, and the method of reference embodiment 1 is tested, and the difference from embodiment 1 is that the electrolyte is replaced with electrolytic paper, which is purchased from Xianhe Co., Ltd., model WJ255-40, and the chloride content in the inspection report is not higher than 1.0PPM (the inspection method is: extraction method+ion chromatography). Take electrolytic paper with different concentrations of chloride ion addition (the chloride ion content is 0PPM, 5PPM, 10PPM respectively, and the specific method is to dissolve sodium chloride in ethanol and drip ethanol into the electrolytic paper), cut it into pieces with clean scissors, weigh 5.0g, and then press it into a test object with a tablet press. The test results of electrolytic paper are shown in Table 4.

[0068] Table 4

[0069]

[0070] Comparative Example 1

[0071] The present embodiment provides a method for determining the halogen content in an electrolyte by an oxygen bomb combustion-turbidimetry method. An electrolyte with a chloride ion content of 50 PPM is prepared, and the composition is the same as that of Example 1. The test is performed with reference to the method of Example 1. The difference from Example 1 is that the absorption liquid is divided into 3 groups: the first group is 30 mL of KOH with a concentration of 20 mmol / L, the second group is a mixed solution of 15 mL of potassium carbonate with a concentration of 20 mmol / L and 15 mL of potassium bicarbonate with a concentration of 20 mmol / L; the third group of absorption liquid is a mixed solution of 10 mL of KOH with a concentration of 20 mmol / L, 10 mL of potassium carbonate with a concentration of 20 mmol / L and 10 mL of potassium bicarbonate with a concentration of 20 mmol / L; the others remain unchanged from Example 1. The test results are shown in Table 5.

[0072] Table 5

[0073]

[0074]

[0075] From the above results, we can see that the absorption liquid is composed of a mixed solution of alkali solution, sodium carbonate and sodium bicarbonate. The test results are highly accurate and have strong applicability.

[0076] Comparative Example 2

[0077] This embodiment provides a method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry. The test is performed with reference to the method of Example 1. The difference from Example 1 is that the volume of the absorption liquid to be tested is adjusted to 5 mL, so that the ratio of the mass of the electrolyte to be tested to the volume of the absorption liquid is 5 g:5 mL. The test results are shown in Table 6.

[0078] Table 6

[0079]

[0080] The volume of the absorption liquid will also affect the test results. Appropriate mass of the electrolyte to be tested and the volume of the absorption liquid can make the test results more accurate.

[0081] Comparative Example 3

[0082] This comparative example provides a method for determining the halogen content of electrolytic paper by oxygen bomb combustion-turbidimetry, and the method of reference Example 2 is used for testing. The difference from Example 2 is that the pretreatment method does not use the oxygen bomb combustion method, but the extraction method. The specific pretreatment is as follows:

[0083] Immerse 5g of electrolytic paper in 200mL of ultrapure water, boil in a water bath at 100℃ for 120min, filter, and then continue to evaporate and concentrate the filtrate in a water bath at 100℃. Finally, make the volume 25mL as the test solution and use the turbidity method for testing. The test results are shown in Table 8. It can be seen that the error between the test results and the standard results is large.

[0084] Table 8

[0085]

[0086]

[0087] The oxygen bomb combustion method absorbs the halogen after the combustion of electrolytic paper, which can significantly improve the accuracy of the halogen in the electrolytic paper.

[0088] From the above results we can see that:

[0089] After pre-treating the sample with a specific absorption liquid using the oxygen bomb combustion method, the chlorine element in the electrolyte sample is detected using the turbidity method, which can significantly improve the detection accuracy and sensitivity of halogens.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry, characterized in that: The steps include: After the S1 electrolyte is dehydrated, it is added to the oxygen bomb device with the absorption liquid, mixed evenly, sealed, and oxygen is introduced to burn in a pure oxygen environment; After the combustion is completed, the mixture is cooled to below 25°C, the gas in the oxygen bomb device is discharged, the absorbed liquid after combustion is combined with the eluent in the oxygen bomb device, and the filtrate after filtration is used as the sample to be tested; Wherein, the absorption liquid contains carbonate, bicarbonate and alkali solution; The electrolyte includes at least one of an electrolyte solution and a solid electrolyte; The mass volume ratio of the electrolyte to the absorption liquid is 1 g: (5-50) mL; S2 uses a turbidity method to test the halogen content in the sample obtained in step S1.

2. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: The composition of the absorption liquid includes the following raw materials: 1-100mmol / L alkali solution, 1-50mmol / L carbonate solution, 1-50mmol / L bicarbonate solution.

3. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: A combustion aid is also added to the oxygen bomb device, and the combustion aid includes at least one of isooctane, anhydrous ethanol, and benzoic acid.

4. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: The electrolyte contains 10-30wt% of solute and 40-90wt% of solvent; And / or, the solid electrolyte includes at least one of electrolytic paper, polypyrrole, polythiophene, and polyaniline; the electrolytic paper includes plant fibers, and the plant fibers include at least one of cellulose, pentosan, and lignin.

5. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: In step S1, oxygen is introduced into the oxygen bomb device to a pressure of 1-5 MPa.

6. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: Satisfies at least one of the following characteristics: 1) The carbonate includes at least one of sodium carbonate and potassium carbonate; 2) The bicarbonate includes at least one of sodium bicarbonate and potassium bicarbonate; 3) The alkali includes at least one of sodium hydroxide and potassium hydroxide.

7. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: The reagent used for eluting the oxygen bomb device is an absorption liquid.

8. The method for determining the halogen content in an electrolyte by oxygen bomb combustion-turbidimetry according to claim 1, characterized in that: The turbidimetry method comprises the following steps: (1) preparing a series of 0-50 PPM halogen ion standard solutions using water-soluble salts containing corresponding halogens; concentrating and fixing the eluent obtained in step S1 to obtain a test solution; (2) Add nitric acid solution to the above-mentioned halogen ion standard solution and the test solution and shake well; then add silver nitrate solution and shake well; after standing for 5 to 20 minutes, test the turbidity with a spectrophotometer and test the absorbance at a wavelength of 450 to 500 nm; obtain a linear curve with the concentration of the halogen ion standard solution as the X-axis and the absorbance as the Y-axis; then substitute the absorbance of the test solution into the relationship obtained by linear curve fitting to calculate the halogen content in the electrolyte.

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