A detection method for judging polyol metal ion content based on conductivity

Abstract

The present application belongs to the technical field of polyol detection, and particularly relates to a detection method for judging the metal ion content of polyol based on conductivity, comprising the following steps: S100, respectively preparing an ethanol aqueous solution and a polyol mixed solution with known metal ion content to be detected; S200, adding the polyol mixed solution with known metal ion content to be detected into the ethanol aqueous solution successively, determining the conductivity value of the ethanol aqueous solution after adding the polyol mixed solution each time, and calculating the conductivity difference of the polyol mixed solution before and after dilution; S300, performing standard curve fitting according to the polyol mixed solution with step concentration and the corresponding conductivity difference, and obtaining a fitting equation; S400, substituting the conductivity difference of the polyol sample determined in the step S200 into the fitting equation obtained in the step S300, and calculating the metal ion content to be detected of the polyol sample. The present application can effectively reduce the test cost and improve the test efficiency.

Description

Technical Field

[0001] This invention belongs to the field of polyol detection technology, specifically relating to a detection method for determining the metal ion content of polyols based on conductivity. Background Technology

[0002] Polyols are an important class of organic and fine chemical raw materials, and their derivatives are high-value-added fine chemical products widely used in pharmaceuticals, polyurethanes, cosmetics, auxiliaries, pesticides, fibers, and plastics. Due to factors such as raw materials, equipment, and catalysts, metal ions are often carried during their production process. However, when polyols react with isocyanates, the metal ions they carry (such as sodium and potassium ions) can catalyze the reaction, increasing side reactions and leading to defects in the products. Therefore, the metal ion content of polyols is an important test required by national standards.

[0003] In existing technologies, the flame photometry method is generally used to test the content of sodium and potassium ions in polyols according to GB / T 12008.4-2009, with a test range of 2ppm-10ppm. The test requires ashing of the sample in a platinum crucible, which is not only time-consuming and requires a lot of equipment with high equipment maintenance and testing costs, but also cumbersome and slow in actual production, which seriously affects the yield of polyols and prolongs the production cycle of polyols and related products.

[0004] Therefore, designing a technology that can quickly test the approximate range of metal ion content in polyols is of great significance for accelerating the production efficiency of polyols and related products and reducing the testing cost of polyols. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for determining the metal ion content of polyols based on conductivity. First, a standard curve is fitted using a polyol mixture with known concentration gradients of the target metal ion and its corresponding conductivity difference. This yields a fitting equation between the target metal ion content and the conductivity difference, representing the correspondence between the target metal ion content and the conductivity difference. Then, following known conductivity difference testing procedures, the conductivity difference of the polyol sample is measured and substituted into the obtained fitting equation to determine the target metal ion content in the polyol sample. This allows for a preliminary assessment of the approximate range of metal ion content in the polyol. The entire testing process primarily utilizes a conductivity meter, pipette, and container equipment. This simplifies the testing equipment, effectively reducing testing costs. Furthermore, it eliminates the need for cumbersome sample processing, significantly shortening testing time and improving efficiency. This facilitates increased production of polyols and related products and can be applied to micro-level and even trace-level testing.

[0006] The technical effects to be achieved by this invention are realized through the following technical solutions:

[0007] The detection method for determining the metal ion content of polyols based on conductivity in this invention includes the following steps: S100, preparing an aqueous ethanol solution and a polyol mixture with a known content of the metal ion to be measured;

[0008] S200. A polyol mixture with a known content of the metal ion to be tested is added to an ethanol aqueous solution in batches. The conductivity of the ethanol aqueous solution is measured after each addition of the polyol mixture with a known content of the metal ion to be tested. The difference in conductivity of the polyol mixture with a known content of the metal ion to be tested before and after dilution is calculated.

[0009] S300. Based on the known concentration gradient of the metal ions to be tested in the polyol mixture and the corresponding conductivity difference, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference.

[0010] S400: Based on the conductivity difference of the polyol sample determined in step S200, substitute it into the fitting equation obtained in step S300 to calculate the content of the metal ion to be tested in the polyol sample.

[0011] Furthermore, step S100 includes the following sub-steps:

[0012] S110. Prepare an ethanol-water solution of a preset concentration using electronic-grade ethanol and ultrapure water, and place it in a polytetrafluoroethylene bottle for later use.

[0013] S120. Using the standard spiking method, add the standard solution of the metal ion to be tested to equal portions of high-purity polyol sample to form a mixed solution with a gradient of metal ion concentrations to be tested. At the same time, add ultrapure water to the mixed solution with low metal ion concentration to keep the ratio of water to polyol constant. After thorough mixing, prepare a polyol mixed solution with known metal ion content to be tested.

[0014] Furthermore, in step 110, the content of a single metal ion in the electronic-grade ethanol is ≤10 ppb, and the solubility of the ethanol aqueous solution is 70%-90%.

[0015] Furthermore, step S200 includes the following sub-steps:

[0016] S210. Weigh the expected amount of ethanol-water solution at room temperature and determine its conductivity EC0.

[0017] S220: Use a pipette to transfer a known amount of polyol mixture containing the metal ion to be tested into an ethanol aqueous solution. After stirring for a period of time, measure the conductivity value as EC1.

[0018] S230. Use a pipette to transfer the expected amount of polyol mixture with known content of the metal ion to be tested into the above mixed solution. After stirring for a period of time, measure the conductivity value as EC2.

[0019] S240. A polyol mixture with a known content of the metal ion to be tested is added n times in sequence, and its conductivity value is measured as ECn, where n≥1 and n is an integer.

[0020] S250. Calculate the difference in conductivity of a polyol mixture with a known content of the metal ion to be tested before and after dilution.

[0021] Furthermore, in steps S220 and S230, the stirring time is 20s-50s.

[0022] Further, in the S250 sub-step, the conductivity difference is calculated using the following formula:

[0023] E x =ECn-EC1;

[0024] Wherein, ECn is the resistivity value of the mixed solution measured after the (n+2)th addition of a polyol mixture with a known content of the metal ion to be tested.

[0025] EC1 is the resistivity value of the mixed solution measured after the first addition of a polyol mixture with a known content of the metal ion to be tested.

[0026] Further, in step 300, based on the known concentration gradient of the metal ion to be tested (100ppb-2000ppb) in the polyol mixture and its corresponding conductivity difference, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference.

[0027] Furthermore, the detection method for determining the metal ion content of polyols based on conductivity in this invention also includes the following step: S500, classifying the metal ion content of the polyol sample according to the obtained metal ion content to be tested.

[0028] Furthermore, step S500 includes the following sub-steps:

[0029] If the content of the metal ion to be tested is <500 ppb, the content of the metal ion to be tested in the polyol sample will be classified as Grade 1.

[0030] If 500ppb≤ the content of the metal ion to be tested < 1000ppb, then the content of the metal ion to be tested in the polyol sample will be divided into two levels.

[0031] If the content of the metal ion to be tested is ≥1000ppb, the content of the metal ion to be tested in the polyol sample will be divided into 3 levels.

[0032] Furthermore, if the content of the metal ion to be tested is Grade 1, the polyol sample will be classified as a superior grade, which meets the requirements for production and use.

[0033] If the content of the metal ion to be tested is level 2, the polyol sample will be further tested to determine whether the polyol sample meets the requirements for production and use.

[0034] If the content of the metal ion to be tested is level 3, the polyol sample will be classified as unqualified and needs to be reprocessed.

[0035] In summary, the present invention has at least the following advantages:

[0036] 1. The method for determining the metal ion content of polyols based on conductivity in this invention firstly uses a polyol mixture with known concentration gradients of the metal ion to be tested and its corresponding conductivity difference to perform standard curve fitting, obtaining the fitting equation between the metal ion content and the conductivity difference, i.e., the correspondence between the metal ion content and the conductivity difference. Then, according to the known conductivity difference testing steps, the conductivity difference of the polyol sample to be tested is measured, and substituted into the obtained fitting equation, the metal ion content in the polyol sample can be obtained, thus preliminarily determining the approximate range of metal ion content in the polyol. The entire testing process mainly uses a conductivity meter, pipette, and container equipment, which not only simplifies the testing equipment and effectively reduces testing costs, but also eliminates the need for cumbersome sample processing, greatly shortening the testing time and effectively improving testing efficiency. This facilitates the increase in the production of polyols and related products and can be applied to micro-level and even trace testing.

[0037] 2. The detection method for determining the metal ion content of polyols based on conductivity in this invention dilutes the metal ions in the polyol into an ethanol aqueous solution to facilitate charge movement and make conductivity testing easier. Since ultrapure water itself contains few metal ions and electronic grade ethanol itself has a low ion content, the background value of the test is lower, and the conductivity value with low metal ion content can be more accurately measured. Attached Figure Description

[0038] Figure 1 This is a schematic flowchart of the detection method for determining the metal ion content of polyols based on conductivity in an embodiment of the present invention.

[0039] Figure 2 This is a fitting curve of the difference between the Na ion content of the polyol and the corresponding conductivity in the embodiments of the present invention. Detailed Implementation

[0040] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0041] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0042] Example 1:

[0043] Please see the appendix Figure 1 This embodiment provides a method for determining the metal ion content of polyols based on conductivity, including the following steps:

[0044] S100, prepare an aqueous ethanol solution and a polyol mixture with a known content of the metal ion to be tested;

[0045] Because metal ions can move directionally in a solution under the influence of an electric field, and the conductivity directly reflects the ease with which metal ions move, the amount of metal ions directly determines the conductivity under given temperature, volume, and medium conditions. The conductivity of an aqueous solution often depends on the amount of solute salt it contains, primarily on the amount of its ionic components. Therefore, the purer the water and the lower the content of soluble salts, the fewer ions can form charges under a given electric field, resulting in lower conductivity. At room temperature (25℃), the conductivity of ultrapure water is 0.1 μS / cm–0.055 μS / cm.

[0046] Because metal ions are difficult to move in polyols and cannot form obvious charge transfer phenomena, their conductivity is difficult to measure using a conductivity meter. Therefore, it is not reliable to determine the content of metal salts by measuring conductivity. Although ethanol is a good solvent for polyols and can dilute and release most of the metal ions in polyols, metal ions are still difficult to exhibit conductivity in pure ethanol.

[0047] Since most metal ions are water-soluble and exhibit significant conductivity in aqueous solutions, but polyols are generally insoluble in water and difficult to dilute directly into water for testing, mixing ethanol with water can dissolve the metal ion salts released by the polyol into the water, making it easier for charges to move and facilitating the determination of the metal ion content in the polyol using conductivity.

[0048] Specifically, the preparation steps for the mixture of ethanol aqueous solution and polyol with known content of the metal ion to be tested are as follows:

[0049] S110. Prepare an ethanol-water solution of a preset concentration using electronic-grade ethanol and ultrapure water, and place it in a polytetrafluoroethylene bottle for later use; further, the single metal ion content of the electronic-grade ethanol is ≤10ppb; since ethanol is mainly used to dilute and dissolve polyols, making soluble ions easier to dissolve, and water is mainly used to dissolve soluble ions in water for easy testing, therefore, preferably, the solubility of the ethanol-water solution is 70%-90%.

[0050] S120. Using the standard spiking method, add the standard solution of the metal ion to be tested to equal portions of high-purity polyol sample to form a mixed solution with a gradient of metal ion concentrations to be tested. At the same time, add ultrapure water to the mixed solution with low metal ion concentration to keep the ratio of water to polyol constant. After thorough mixing, prepare a polyol mixed solution with known metal ion content to be tested.

[0051] S200. A polyol mixture with a known predicted amount of the metal ion to be tested is successively added to an ethanol-water solution. The conductivity of the ethanol-water solution is measured after each addition of the polyol mixture with a known predicted amount of the metal ion to be tested, and the difference in conductivity before and after dilution is calculated. Specifically, the difference in conductivity before and after dilution can be achieved through the following steps:

[0052] S210. Under room temperature (25℃) conditions, weigh the expected amount of ethanol aqueous solution and determine its conductivity EC0; wherein, the amount of ethanol aqueous solution weighed can be selected according to the actual test needs, preferably 80ml-95ml, which is convenient for calculation and can be matched with the capacity of the container.

[0053] S220: Use a pipette to transfer a known amount of polyol mixture containing the metal ion to be tested into an ethanol aqueous solution. Stir for 20-50 seconds and then measure the conductivity value as EC1.

[0054] S230. Use a pipette to transfer the expected amount of polyol mixture with known content of the metal ion to be tested, add it to the above mixed solution, stir for 20s-50s, and then measure the conductivity value as EC2.

[0055] In steps S220 and S230, the amount of polyol mixture transferred can be selected according to the concentration of polyol to be diluted and the number of transfers, preferably 0.5ml-2ml.

[0056] S240. Add a polyol mixture with a known content of the metal ion to be tested n times in sequence, and measure its conductivity value ECn, where n≥1 and n is an integer. The purpose of adding multiple times is to monitor whether the conductivity changes during the dilution process, and at the same time increase the stirring time to ensure that the polyol is fully dissolved and the ions are fully released. The actual number of additions can be set according to the concentration of the polyol to be diluted.

[0057] S250. Calculate the difference in conductivity of the polyol mixture before and after dilution for a known concentration of the metal ion to be tested; specifically, the formula for calculating the difference in conductivity before and after dilution is:

[0058] E x =ECn-EC1;

[0059] Wherein, ECn is the resistivity value of the mixed solution measured after the (n+2)th addition of a polyol mixture with a known content of the metal ion to be tested.

[0060] EC1 is the resistivity value of the mixed solution measured after the first addition of a polyol mixture with a known content of the metal ion to be tested.

[0061] S300. Based on the known concentration gradients of the metal ions to be tested in polyol mixtures and their corresponding conductivity differences, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference. Further, based on the known concentration gradients of the metal ions to be tested in polyol mixtures from 100ppb to 2000ppb and their corresponding conductivity differences, a standard curve is fitted. Preferably, based on the known concentration gradients of the metal ions to be tested in polyol mixtures of 100ppb, 200ppb, 300ppb, 400ppb, 500ppb, 1000ppb, and 2000ppb and their corresponding conductivity differences, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference.

[0062] S400: Based on the conductivity difference of the polyol sample determined in step S200, substitute it into the fitting equation obtained in step S300 to calculate the content of the metal ion to be tested in the polyol sample.

[0063] The detection method in this embodiment first uses a polyol mixture with known concentrations of the target metal ion and its corresponding conductivity difference to perform standard curve fitting, obtaining the fitting equation between the target metal ion content and the conductivity difference, i.e., the correspondence between the target metal ion content and the conductivity difference. Then, according to the known conductivity difference testing steps, the conductivity difference of the target polyol sample is measured, and substituted into the obtained fitting equation to obtain the target metal ion content in the polyol sample, thus preliminarily determining the approximate range of the metal ion content in the polyol. The entire testing process mainly uses a conductivity meter, pipette, and container equipment, which not only simplifies the testing equipment and effectively reduces testing costs, but also eliminates the need for cumbersome sample processing, greatly shortening the testing time and effectively improving testing efficiency. This facilitates the increase in the production of polyols and related products and can be applied to micro-level and even trace testing. In addition, by diluting the metal ions in the polyol into an aqueous ethanol solution, the charge can be moved, which facilitates the measurement of conductivity. Since ultrapure water itself contains few metal ions and electronic grade ethanol itself has a low ion content, the background value of the test is lower, and the conductivity value with low metal ion content can be more accurately measured.

[0064] Example 2:

[0065] Please see the appendix Figure 1 This embodiment provides a method for determining the metal ion content of polyols based on conductivity, which is the same as in Embodiment 1 and includes the following steps:

[0066] S100, prepare an aqueous ethanol solution and a polyol mixture with a known content of the metal ion to be tested;

[0067] S200. A polyol mixture with a known content of the metal ion to be tested is added to an ethanol aqueous solution in batches. The conductivity of the ethanol aqueous solution is measured after each addition of the polyol mixture with a known content of the metal ion to be tested. The difference in conductivity of the polyol mixture with a known content of the metal ion to be tested before and after dilution is calculated.

[0068] S300. Based on the known concentration gradient of the metal ions to be tested in the polyol mixture and the corresponding conductivity difference, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference.

[0069] S400: Based on the conductivity difference of the polyol sample determined in step S200, substitute it into the fitting equation obtained in step S300 to calculate the content of the metal ion to be tested in the polyol sample.

[0070] The main difference lies in the fact that the detection method for determining the metal ion content of polyols based on conductivity in this embodiment further includes the following steps:

[0071] S500. Based on the obtained content of the metal ions to be tested in the polyol samples, the content of the metal ions to be tested in the polyol samples is classified into grades. Specifically, the classification of metal ion content grades can be achieved through the following steps:

[0072] If the content of the metal ion to be tested is <500ppb, the content of the metal ion to be tested in the polyol sample will be classified as Grade 1, and the polyol sample will be classified as a superior grade, which meets the requirements for production and use.

[0073] If 500ppb≤ the content of the metal ion to be tested < 1000ppb, the content of the metal ion to be tested in the polyol sample will be divided into two levels. At the same time, the polyol sample will be further tested to determine whether the polyol sample meets the requirements for production and use.

[0074] If the content of the metal ion to be tested is ≥1000ppb, the content of the metal ion to be tested in the polyol sample will be classified into three levels, and the polyol sample will be classified as unqualified and needs to be reprocessed.

[0075] The detection method in this embodiment, based on Example 1, classifies polyol samples according to the content of the metal ions to be tested. This method can quickly and efficiently determine whether polyol samples meet the requirements for production and use, thus facilitating the shortening of the production cycle of polyols and corresponding products.

[0076] Example 3:

[0077] This embodiment provides a method for determining the Na ion content of polyols based on conductivity, including the following steps:

[0078] 1. Prepare a 90% ethanol-water solution using electronic-grade ethanol and ultrapure water, and store it in a 5L polytetrafluoroethylene bottle for later use.

[0079] 2. Weigh seven 99ml portions of high-purity polyol sample and place them in separate 150ml PE cups, labeling them ①②③④⑤⑥⑦. Using the standard addition method, pipette 1ml of a 200ppm Na ion concentration standard solution and add it to the high-purity polyol in cup ⑦. Stir until well mixed to obtain a polyol mixed solution with a Na ion concentration of 2000ppb. Pipette 0.5ml of the 200ppm Na ion concentration standard solution and add it to the high-purity polyol in cup ⑥. Simultaneously, add 0.5ml of ultrapure water to the high-purity polyol in cup ⑥ and mix thoroughly to obtain a solution with a Na ion concentration of 1000ppb. A polyol mixed solution with Na ion concentration; similarly, ultrapure water is added to the mixed solution with low Na ion concentration to maintain the ratio of water to polyol. The mixture is stirred thoroughly to prepare a mixed solution of polyol and water with known Na ion concentration gradient. After addition, the Na ion content in PE cups numbered ①②③④⑤⑥⑦ is 100ppb, 200ppb, 300ppb, 400ppb, 500ppb, 1000ppb, and 2000ppb, respectively.

[0080] 3. Under room temperature (25℃) conditions, weigh 90 ml of ethanol-water solution and measure its conductivity (EC0). Pipette 1 ml of a mixed solution ① with a Na ion content of 100 ppb and add it to the ethanol-water solution. After stirring for 30 seconds, measure the conductivity (EC1). Pipette another 1 ml of the mixed solution ① with a Na ion content of 100 ppb and add it to the previous mixed solution. After stirring for 30 seconds, measure the conductivity (EC2). Continue adding 10 ml of the mixed solution ① with a Na ion content of 100 ppb to the mixed solution and measure its conductivity up to EC10. Perform the same procedure three times for the polyol solution with a Na ion content of 100 ppb. Then, calculate the conductivity difference before and after dilution using the formula: E x =EC10-EC1, calculate the difference in conductivity before and after three dilutions of a polyol solution with a Na ion content of 100 ppb, as shown in Table 1.

[0081] Table 1. Conductivity values ​​and conductivity differences (Na ion content 100 ppb)

[0082]

[0083] 4. At room temperature (25℃), weigh 90 ml of ethanol-water solution and measure its conductivity (EC0). Pipette 1 ml of mixed solution ② with a Na ion content of 200 ppb and add it to the ethanol-water solution. After stirring for 30 seconds, measure the conductivity (EC1). Pipette another 1 ml of mixed solution ② with a Na ion content of 200 ppb and add it to the previous mixed solution. After stirring for 30 seconds, measure the conductivity (EC2). Continue adding 10 ml of mixed solution ② with a Na ion content of 200 ppb to the mixed solution and measure the conductivity up to EC10. Perform the same procedure three times for the polyol solution with a Na ion content of 200 ppb. Then, calculate the conductivity difference before and after dilution using the formula: E x =EC10-EC1, calculate the difference in conductivity before and after three dilutions of a polyol solution with a Na ion content of 200 ppb, as shown in Table 2.

[0084] Table 2. Conductivity values ​​and conductivity differences (Na ion content 200 ppb)

[0085]

[0086]

[0087] 5. Similarly, polyol mixed solutions with known Na ion concentrations of 300ppb, 400ppb, 500ppb, 1000ppb, and 2000ppb were tested sequentially, resulting in E3, E4, E5, E6, and E7. The results are shown in Table 3-7.

[0088] Table 3. Conductivity values ​​and conductivity differences (Na ion content 300 ppb)

[0089]

[0090] Table 4. Conductivity values ​​and conductivity differences (Na ion content 400 ppb)

[0091]

[0092] Table 5. Conductivity values ​​and conductivity differences (Na ion content 500 ppb)

[0093]

[0094] Table 6. Conductivity values ​​and conductivity differences (Na ion content 1000 ppb)

[0095]

[0096] Table 7 Conductivity values ​​and conductivity differences (Na ion content 2000 ppb)

[0097]

[0098] 6. The difference between the Na ion content and the corresponding conductivity E in polyols. x Prepare a standard curve and simultaneously perform standard curve fitting to obtain, as shown below. Figure 2 The fitted curve shown yields the difference E between Na ion content and conductivity. x The fitting equation is: Y = 0.00002X + 0.005, where Y is the difference in conductivity and X is the content of the metal ion to be measured; it can be seen that the concentration of Na ions in polyol is linearly correlated with the difference in conductivity.

[0099] 7. At room temperature (25℃), weigh 90 ml of ethanol-water solution and measure its conductivity (EC0). Pipette 1 ml of the polyol sample 1 to be tested and add it to the ethanol-water solution. After stirring for 30 seconds, measure the conductivity (EC1). Pipette another 1 ml of the polyol sample 1 to be tested and add it to the previous mixture. After stirring for 30 seconds, measure the conductivity (EC2). Continue adding 10 ml of the polyol sample 1 to the mixture and measure its conductivity up to EC10. Repeat this process three times. Then, calculate the conductivity difference before and after dilution using the formula: E... x =EC10-EC1, calculate the difference in conductivity before and after three dilutions of the polyol sample 1, as shown in Table 8.

[0100] Table 8. Conductivity values ​​and conductivity differences (for polyol sample 1).

[0101]

[0102] According to Table 8, the average value of the conductivity difference of the three polyol samples 1 was calculated to be E8 = 0.0137 μS / cm, i.e., Y = 0.0137 μS / cm. Substituting this into the fitting equation Y = 0.00002X + 0.005, we get X = 660. That is, the Na ion content in the polyol sample 1 is 660 ppb, which is between 500 ppb and 1000 ppb. Therefore, it is necessary to test the polyol sample 1 again to accurately determine the actual Na ion content in the polyol sample 1.

[0103] 8. The conductivity and conductivity difference of the polyol sample 2 were measured three times in the same manner, as shown in Table 9.

[0104] Table 9. Conductivity values ​​and conductivity differences (for polyol sample 2).

[0105]

[0106] According to Table 9, the average value of the conductivity difference of the three polyol samples 2 was calculated to be E9 = 0.001 μS / cm, i.e., Y = 0.001 μS / cm. Substituting this into the fitting equation Y = 0.00002X + 0.005, we get X = 25. That is, the Na ion content in polyol sample 2 is 25 ppb, which is less than 500 ppb. Therefore, polyol sample 2 is classified as a superior grade product, which meets the requirements for production and use.

[0107] 9. The Na ion content of polyol samples 1 and 2 was tested by ICP test. The actual ion content of polyol samples 1 and 2 is shown in Table 10.

[0108]

[0109]

[0110] As shown in Table 10, the Na ion content of polyol sample 1 is 404 ppb, and the Na ion content of polyol sample 2 is less than 100 ppb. Therefore, the detection method of polyol metal ion content based on conductivity in this invention can quickly and effectively determine the metal ion content in polyol samples, thereby efficiently determining whether polyol samples meet the requirements for production and use, and shortening the production cycle of polyols and corresponding products.

[0111] As can be seen from the technical solutions of the above embodiments, the present invention provides a detection method for determining the metal ion content of polyols based on conductivity. Not only is the testing equipment simple and can effectively reduce testing costs, but it also eliminates the need for cumbersome processing of test samples, which can greatly shorten the testing time and effectively improve testing efficiency. This facilitates the increase in the production of polyols and related products and can be applied to micro-level testing and even trace testing.

[0112] Although the description of the invention has been given in conjunction with the specific embodiments described above, it will be apparent to those skilled in the art that many substitutions, modifications, and variations can be made based on the foregoing. Therefore, all such substitutions, modifications, and variations are included within the spirit and scope of the appended claims.

Claims

1. A method for determining the metal ion content of polyols based on conductivity, characterized in that, Includes the following steps, S100, prepare an aqueous ethanol solution and a polyol mixture with a known content of the metal ion to be tested; S200. A polyol mixture with a known content of the metal ion to be tested is added to an ethanol aqueous solution in batches. The conductivity of the ethanol aqueous solution is measured after each addition of the polyol mixture with a known content of the metal ion to be tested. The difference in conductivity of the polyol mixture with a known content of the metal ion to be tested before and after dilution is calculated. S300. Based on the known concentration gradient of the metal ions to be tested in the polyol mixture and the corresponding conductivity difference, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference. S400: Measure the conductivity difference of the polyol sample according to step S200, substitute it into the fitting equation obtained in step S300, and calculate the content of the metal ion to be tested in the polyol sample. Step S200 includes the following sub-steps: S210. Weigh the expected amount of ethanol-water solution at room temperature and determine its conductivity EC0. S220: Pipette a volume of polyol mixture with known metal ion content to be measured into an ethanol aqueous solution, stir for a period of time, and then measure the conductivity value as EC1. S230. Use a pipette to transfer the expected amount of polyol mixture with known content of the metal ion to be tested into the above mixed solution. After stirring for a period of time, measure the conductivity value as EC2. S240. A polyol mixture with a known content of the metal ion to be tested is added n times in sequence, and its conductivity value is measured as ECn, where n≥1 and n is an integer. S250. Calculate the difference in conductivity of a polyol mixture with a known content of the metal ion to be tested before and after dilution. In sub-step S250, the conductivity difference is calculated using the following formula: TO x =ECn-EC1; Wherein, ECn is the resistivity value of the mixed solution measured after the (n+2)th addition of a polyol mixture with a known content of the metal ion to be tested. EC1 is the resistivity value of the mixed solution measured after the first addition of a polyol mixture with a known content of the metal ion to be tested.

2. The detection method according to claim 1, characterized in that, Step S100 includes the following sub-steps: S110. Prepare an ethanol-water solution of a preset concentration using electronic-grade ethanol and ultrapure water, and place it in a polytetrafluoroethylene bottle for later use. S120. Using the standard spiking method, add the standard solution of the metal ion to be tested to equal portions of high-purity polyol sample to form a mixed solution with a gradient of metal ion concentrations to be tested. At the same time, add ultrapure water to the mixed solution with low metal ion concentration to keep the ratio of water to polyol constant. After thorough mixing, prepare a polyol mixed solution with known metal ion content to be tested.

3. The detection method according to claim 2, characterized in that, In step 110, the content of a single metal ion in electronic-grade ethanol is ≤10ppb, and the solubility of the ethanol aqueous solution is 70%-90%.

4. The detection method according to claim 1, characterized in that, In steps S220 and S230, the stirring time is 20s-50s.

5. The detection method according to claim 1, characterized in that, In step 300, based on the known concentration gradient of the metal ion to be tested (100ppb-2000ppb) in the polyol mixture and its corresponding conductivity difference, a standard curve is fitted to obtain the fitting equation between the metal ion content to be tested and the conductivity difference.

6. The detection method according to claim 1, characterized in that, It also includes the following steps, S500. Based on the obtained content of the metal ions to be tested in the polyol samples, classify the content of the metal ions to be tested in the polyol samples into grades.

7. The detection method according to claim 6, characterized in that, The S500 step includes the following sub-steps: If the content of the metal ion to be tested is <500 ppb, the content of the metal ion to be tested in the polyol sample will be classified as Grade 1. If 500ppb≤ the content of the metal ion to be tested < 1000ppb, then the content of the metal ion to be tested in the polyol sample will be divided into two levels. If the content of the metal ion to be tested is ≥1000ppb, the content of the metal ion to be tested in the polyol sample will be divided into 3 levels.

8. The detection method according to claim 7, characterized in that, If the content of the metal ions to be tested is Grade 1, then the polyol sample will be classified as a superior grade, which meets the requirements for production and use. If the content of the metal ion to be tested is level 2, the polyol sample will be further tested to determine whether the polyol sample meets the requirements for production and use. If the content of the metal ion to be tested is level 3, the polyol sample will be classified as unqualified and needs to be reprocessed.

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