Method for determining content of p-tert-butyl benzoic acid and barium in PVC heat stabilizer

Abstract

This invention discloses a method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers, comprising the following steps: S1, mixing the stabilizer sample with dilute sulfuric acid, allowing it to stand, adding pure water to obtain a first product with distinct stratification; S2, filtering and drying the aqueous layer and precipitate of the first product to obtain a second product, which is then weighed; S3, washing the second product multiple times with ethanol to obtain a third product, which is then weighed. The mass of the third product is the mass of barium sulfate, and the barium content in the stabilizer sample is calculated. The difference between the mass of the second product and the mass of the third product is the content of p-tert-butylbenzoic acid in the precipitate; S4, determining the content of free p-tert-butylbenzoic acid using gas chromatography-mass spectrometry (GC-MS). The content of p-tert-butylbenzoic acid is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid. This invention can effectively detect the content of some organic acids in heat stabilizers.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, specifically to a method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers. Background Technology

[0002] Polyvinyl chloride (PVC) is one of the major general-purpose plastics, possessing advantages such as high strength, corrosion resistance, flame retardancy, good insulation, and transparency. Its products are widely used in construction, chemical, electrical appliance, and packaging industries. However, PVC suffers from poor thermal stability, therefore, appropriate heat stabilizers must be added during processing to inhibit its thermal degradation. Currently, commonly used heat stabilizers mainly include lead salts, organotin compounds, and metal (barium, cadmium, calcium, zinc, etc.) soaps. Among these, lead salts and barium and cadmium soaps have better performance. During use, the soaps formed by the combination of metals and organic acids directly contact PVC. After PVC thermoforming, the stabilizer reacts with the hydrogen chloride released from the partial decomposition of PVC, easily converting into corresponding metal chlorides, thus terminating or inhibiting PVC decomposition and enhancing thermal stability.

[0003] Metallic soaps, due to their simple production process, reasonable price, odorless nature, and lubricant properties, have long been the primary heat stabilizer for soft PVC processing and are also used in some rigid PVC processing. Practical metallic soap heat stabilizers are all metal soap complexes with different properties, and their performance is closely related to the content of each component. Among these, the content of organic acids and metals in the stabilizer is crucial to its performance. Currently, the production of PVC heat stabilizers in my country is continuously increasing, but there are no unified national or industry standards to regulate product quality. Furthermore, there are few reports on methods for detecting the content of components in heat stabilizers, and the formulations of PVC profiles and heat stabilizers are not entirely the same, leading to significant measurement errors. Existing single conventional testing methods such as HPLC, IC, and GCMS suffer from problems such as complex sample preparation and large differences in quantitative results. Therefore, there is a need to find a simpler, faster, and more convenient method to effectively detect the content of certain organic acids in heat stabilizers. Summary of the Invention

[0004] The main objective of this invention is to provide a method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers, which aims to enable rapid, simple, and effective detection of the content of p-tert-butylbenzoic acid and barium in heat stabilizers.

[0005] To achieve the above objectives, this invention proposes a method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers, comprising the following steps:

[0006] S1. Mix the stabilizer sample with dilute sulfuric acid, let it stand, add pure water, and obtain the first product with obvious stratification.

[0007] S2. The upper oil layer of the first product is sucked out with a dropper and stored for later testing. The water layer and sediment of the first product are filtered and dried to obtain the second product. The weight of the second product is weighed and recorded.

[0008] S3. Wash the second product with ethanol multiple times to remove the p-tert-butylbenzoic acid precipitated with barium sulfate, and obtain the third product. Weigh and record its mass. The mass of the third product is the mass of barium sulfate. Calculate the barium content in the stabilizer sample from the mass of barium sulfate using the formula. The difference between the mass of the second product recorded in step S2 and the mass of the third product recorded in step S3 is the p-tert-butylbenzoic acid content in the precipitate.

[0009] S4. Filter the upper layer of oil extracted by the dropper with an organic filter membrane to obtain an oil sample. Measure the content of free p-tert-butylbenzoic acid in the oil sample using a gas chromatography-mass spectrometry (GC-MS) instrument. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid.

[0010] Optionally, the determination of free p-tert-butylbenzoic acid content using the gas chromatography-mass spectrometry (GC-MS) instrument includes the following steps:

[0011] S41. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution;

[0012] S42. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations;

[0013] S43. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6;

[0014] S44. Use a gas chromatography-mass spectrometry (GC-MS) instrument to determine the chromatographic peak areas of the standards and samples. Plot a standard curve with the concentrations of standards 1-5 on the x-axis and the chromatographic peak areas measured by the GC-MS instrument on the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6.

[0015] Optionally, in step S41, the organic solvent is at least one of dichloromethane, petroleum ether, and methanol.

[0016] Optionally, in step S43, the oil sample is taken in a mass of 0.01 to 0.1 g and dispersed in 10 to 20 g of organic solvent.

[0017] Optionally, in step S1, the mass fraction of the dilute sulfuric acid is 10% to 30%, and the mass ratio of the stabilizer sample to sulfuric acid is 2 to 10: 1 to 5.

[0018] Optionally, in step S1, the mass ratio of the stabilizer sample to sulfuric acid is 2-10:1-5.

[0019] Optionally, in step S1, the settling time is 20 to 60 minutes.

[0020] Optionally, in step S2, slow-speed filter paper is used for filtration, and the drying temperature is 40-80°C.

[0021] Optionally, in step S3, the washing is performed 1 to 5 times.

[0022] Optionally, in step S4, the test conditions for the gas chromatography-mass spectrometry (GC-MS) to determine the standard and sample are as follows:

[0023] Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm;

[0024] Detector: Flame ionization detector;

[0025] Testing chamber temperature: 300℃;

[0026] Vaporization chamber temperature: 300℃;

[0027] Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min;

[0028] Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0 mL / min;

[0029] Fuel gas: Hydrogen, purity ≥ 99.999%, flow rate 30 mL / min;

[0030] Combustion aid: Air, flow rate 400 mL / min.

[0031] The present invention has the following beneficial effects:

[0032] (1) In the technical solution provided by the present invention, the amount of organic solvent used is small, which saves resources, the operation method is convenient and fast, and it is easy to achieve batch processing;

[0033] (2) The sample pretreatment process is simple, requiring only simple mixing of the reactants;

[0034] (3) The filtration process is short and efficient. After adding solvent, the target substance in the oil can be quickly transferred without much manpower or material resources.

[0035] (4) The reaction process is carried out at a low temperature and is less dangerous. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is the infrared spectrum of the precipitate produced in Example 1 of the present invention;

[0038] Figure 2 This is a gas chromatogram of p-tert-butylbenzoic acid in Example 1 of the present invention.

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Given the limited existing methods for detecting the content of components in heat stabilizers, and the fact that conventional single testing methods such as HPLC, IC, and GCMS suffer from problems such as complex sample preparation and large discrepancies in quantitative results, this invention proposes a method for determining the content of some organic acids and metals in PVC heat stabilizers. This method aims to better adjust the formulation and improve the performance of the stabilizer, while also providing a new analytical approach for the detection of other components in heat stabilizers.

[0042] This invention proposes a method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers, comprising the following steps:

[0043] S1. Mix the stabilizer sample with dilute sulfuric acid, let it stand, add pure water, and obtain the first product with obvious stratification.

[0044] In this step, the mass fraction of the dilute sulfuric acid is 10% to 30%, and the mass ratio of the stabilizer sample to sulfuric acid is 2 to 10: 1 to 5. The standing time is 20 to 60 minutes. By adding an appropriate amount of sulfuric acid, the reaction is made sufficient, and the product can be clearly separated into layers after standing.

[0045] S2. The upper oil layer of the first product is sucked out with a dropper and stored for later testing. The water layer and sediment of the first product are filtered and dried to obtain the second product. The weight of the second product is weighed and recorded.

[0046] In this step, slow-speed filter paper is used to filter the water layer and the sediment. After filtration, the product is placed in an oven for drying at a temperature of 40–80°C.

[0047] S3. Wash the second product with ethanol multiple times to remove the p-tert-butylbenzoic acid precipitated with barium sulfate, and obtain the third product. Weigh and record its mass. The mass of the third product is the mass of barium sulfate. Calculate the barium content in the stabilizer sample from the mass of barium sulfate using the formula. The difference between the mass of the second product recorded in step S2 and the mass of the third product recorded in step S3 is the p-tert-butylbenzoic acid content in the precipitate.

[0048] In this step, the washing is performed 1 to 5 times.

[0049] S4. Filter the upper layer of oil extracted by the dropper with an organic filter membrane to obtain an oil sample. Measure the content of free p-tert-butylbenzoic acid in the oil sample using a gas chromatography-mass spectrometry (GC-MS) instrument. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid.

[0050] In this step, the test conditions for measuring the standard and sample using the gas chromatography-mass spectrometry (GC-MS) are as follows:

[0051] Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm; Detector: Flame ionization detector; Detector temperature: 300℃; Vaporization chamber temperature: 300℃; Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min; Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0mL / min; Fuel gas: Hydrogen, purity ≥99.999%, flow rate 30mL / min; Combustion oxidizer: Air, flow rate 400mL / min.

[0052] The technical solution provided by this invention features a simple sample pretreatment process. It only requires simple mixing of reactants to obtain products with different layers, followed by weighing and further processing to obtain the content of p-tert-butylbenzoic acid and barium. The determination process uses a small amount of organic solvent, saving resources. The operation method is convenient and fast, and it is easy to achieve batch processing. The filtration process is short and efficient. After adding solvent, the target substances in the oil can be quickly transferred without much manpower or material resources. Furthermore, the reaction process has a low temperature and low risk.

[0053] Specifically, the determination of free p-tert-butylbenzoic acid using the gas chromatography-mass spectrometry (GC-MS) instrument includes the following steps:

[0054] S41. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution;

[0055] In this step, the organic solvent is at least one of dichloromethane, petroleum ether, and methanol.

[0056] S42. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations;

[0057] S43. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6;

[0058] In this step, to facilitate the calculation of the concentration of free p-tert-butylbenzoic acid, a certain amount of free p-tert-butylbenzoic acid is dissolved in a certain mass of organic solvent. Preferably, the mass of the oil sample is 0.01 to 0.1 g, and it is dispersed in 10 to 20 g of organic solvent.

[0059] S44. Use a gas chromatography-mass spectrometry (GC-MS) instrument to determine the chromatographic peak areas of the standards and samples. Plot a standard curve with the concentrations of standards 1-5 on the x-axis and the chromatographic peak areas measured by the GC-MS instrument on the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6.

[0060] This embodiment provides the implementation steps of a specific measurement method:

[0061] (1) Sample processing

[0062] 5.17 g of stabilizer sample and 3.57 g of 20% dilute sulfuric acid were placed in a beaker and allowed to stand for 30 min. A small amount of pure water was then added to cause the product to separate into distinct layers. The upper oil layer was aspirated with a dropper and stored. The aqueous layer and the precipitate were filtered through slow-speed filter paper. The product was then dried in a 60°C oven for 2 h. After drying, the product was weighed and the first mass was recorded. The dried product was washed three times with ethanol, and the precipitate was weighed again and the second mass was recorded. The upper oil layer was filtered through a 0.22 μm organic filter membrane and then subjected to gas chromatography-mass spectrometry (GC-MS) to determine the free p-tert-butylbenzoic acid content.

[0063] (2) External standard method for quantification

[0064] Disperse the standard p-tert-butylbenzoic acid reagent in dichloromethane solvent, and denote this as the diluent. Prepare five standard working solutions of different concentrations from the diluent, numbered 1, 2, 3, 4, and 5, with mass fractions of 0.1%, 0.125%, 0.167%, 0.25%, and 0.5%, respectively. Plot the standard working curve y = ax + b with concentration as the x-axis and peak area as the y-axis.

[0065] The separated oil sample was dispersed in dichloromethane solvent, numbered 6, and its content was recorded as C0. The peak area obtained after chromatographic analysis of the sample was substituted into the working curve to calculate the concentration C of p-tert-butylbenzoic acid in the test solution.

[0066] Calculate the content (%) of p-tert-butylbenzoic acid in the upper layer oil using the following formula (1):

[0067]

[0068] In the formula:

[0069] C: Content of p-tert-butylbenzoic acid in the test solution, %;

[0070] C0: Oil content in the sample, %;

[0071] W 上 The content of p-tert-butylbenzoic acid in the upper layer oil, %.

[0072] The final test result of this test method is the average of three parallel determinations, and the relative standard deviation of the parallel determination results is less than 10%.

[0073] (3) Calculation of the contents of barium metal and p-tert-butylbenzoic acid in the sample

[0074] Taking advantage of the fact that p-tert-butylbenzoic acid is soluble in ethanol, the sample processing example involves washing the sample multiple times with ethanol to remove the p-tert-butylbenzoic acid that precipitates along with barium sulfate. The mass recorded during the second weighing is the mass of barium sulfate.

[0075] The content (%) of barium in the stabilizer sample can be calculated using formula (2) based on the mass of barium sulfate:

[0076]

[0077] In the formula:

[0078] m2: Mass recorded during the second weighing, in grams;

[0079] M: Mass of stabilizer sample, g;

[0080] W Ba : The content of metallic barium in the sample, %.

[0081] The total content of p-tert-butylbenzoic acid in the stabilizer sample is the sum of the content in the precipitate and the content in the oil phase.

[0082] The difference between the first and second weighings is the content of p-tert-butylbenzoic acid in the precipitate.

[0083] Calculate the total content (%) of p-tert-butylbenzoic acid in the stabilizer sample according to formula (3):

[0084]

[0085] In the formula:

[0086] m1: The mass recorded during the first weighing, in grams;

[0087] m2: Mass recorded during the second weighing, in grams;

[0088] W 上 The content of p-tert-butylbenzoic acid in the upper layer oil, %.

[0089] W 总 : Total content of p-tert-butylbenzoic acid in the stabilizer sample, %.

[0090] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0091] Example 1: Method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers

[0092] (1) Sample processing

[0093] 4.99 g of stabilizer sample and 3.4 g of 20% dilute sulfuric acid were placed in a beaker and allowed to stand for 30 min. A small amount of pure water was then added to cause the product to separate into distinct layers. The upper oil layer was collected using a dropper for gas chromatography-mass spectrometry (GC-MS) analysis. The resulting precipitate was analyzed by infrared spectroscopy. Figure 1After filtering the aqueous layer and precipitate with slow-speed filter paper, the product was dried in a 60℃ oven for 2 hours. After drying, the product was weighed and the first mass was recorded. The dried product was washed twice with ethanol, and the resulting precipitate was weighed again and the second mass was recorded. The upper oil layer was filtered through a 0.22μm organic filter membrane, and the free p-tert-butylbenzoic acid was quantitatively tested. The test results are shown in Table 1 below.

[0094] Table 1. Record of the mass of two precipitates generated during the reaction of the stabilizer sample with sulfuric acid.

[0095] sample weight / g 20% sulfuric acid / g First weighing / g Second weighing / g Difference / g stabilizer 4.99 3.4 0.5 0.4 0.1

[0096] The mass recorded during the second weighing is the mass of barium sulfate. The content of barium in the sample is calculated according to formula (2) and compared with the actual content. The results are shown in Table 2 below.

[0097] Table 2 Calculated values ​​of barium content in stabilizer samples

[0098]

[0099] (2) External standard method for quantification

[0100] Dissolve the standard p-tert-butylbenzoic acid in dichloromethane solvent, and denote this as the diluent. Prepare five standard working solutions of different concentrations from the diluent, numbered 1, 2, 3, 4, and 5, with mass fractions of 0.105%, 0.129%, 0.163%, 0.246%, and 0.491%, respectively. Plot a standard working curve y = ax + b with concentration as the x-axis and peak area as the y-axis. Disperse the separated oil sample in dichloromethane solvent, numbered 6, and denote the content as C0. Perform gas chromatography-mass spectrometry (GC-MS) analysis on the oil sample to obtain... Figure 2 After substituting the peak areas obtained from the chromatographic analysis of the sample into the working curve, the concentration C of p-tert-butylbenzoic acid in the test solution was calculated. The calculation table of p-tert-butylbenzoic acid content in the upper oil layer of the stabilizer sample is as follows.

[0101] Table 3. Calculation of p-tert-butylbenzoic acid content in the upper layer oil of stabilizer samples.

[0102]

[0103] (3) Calculation of the content of p-tert-butylbenzoic acid in the sample

[0104] The total content of p-tert-butylbenzoic acid in the stabilizer sample is calculated according to formula (3) as the sum of the content in the precipitate and the content in the oil phase. The content of each component is recorded in Table 4 below.

[0105] Table 4. Record of p-tert-butylbenzoic acid content in precipitate and oil phase

[0106]

[0107] Based on the test results, it can be seen that the measured values ​​of p-tert-butylbenzoic acid and barium content in PVC heat stabilizers are very close to the actual values, and this method can be used for determination.

[0108] In summary, the method for determining the content of p-tert-butylbenzoic acid and barium in PVC heat stabilizers proposed in this invention can effectively detect the content of barium and tert-butylbenzoic acid in stabilizer samples. Moreover, this method is convenient, rapid, and easy to implement in batch processing.

[0109] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for determining the content of p-tert-butylbenzoic acid and barium in a PVC heat stabilizer, characterized in that, Includes the following steps: S1. Mix the stabilizer sample with dilute sulfuric acid, let it stand, add pure water, and obtain the first product with obvious stratification. S2. The upper oil layer of the first product is sucked out with a dropper and stored for later testing. The water layer and sediment of the first product are filtered and dried to obtain the second product. The weight of the second product is weighed and recorded. S3. Wash the second product with ethanol multiple times to remove the p-tert-butylbenzoic acid precipitated with barium sulfate, and obtain the third product. Weigh and record its mass. The mass of the third product is the mass of barium sulfate. Calculate the barium content in the stabilizer sample from the mass of barium sulfate using the formula. The difference between the mass of the second product recorded in step S2 and the mass of the third product recorded in step S3 is the p-tert-butylbenzoic acid content in the precipitate. S4. Filter the upper layer of oil extracted by the dropper with an organic filter membrane to obtain an oil sample. Determine the content of free p-tert-butylbenzoic acid in the oil sample by gas chromatography. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid.

2. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, The determination of free p-tert-butylbenzoic acid using gas chromatography includes the following steps: S41. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution; S42. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations; S43. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6; S44. Use a gas chromatograph to determine the chromatographic peak area of ​​the standard and the sample. Plot a standard curve with the concentration of standards 1-5 as the x-axis and the chromatographic peak area determined by the gas chromatograph as the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6.

3. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 2, characterized in that, In step S41, the organic solvent is at least one of dichloromethane, petroleum ether, and methanol.

4. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S43, the oil sample is taken in a mass of 0.01~0.1 g and dispersed in 10~20 g of organic solvent.

5. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S1, the mass fraction of the dilute sulfuric acid is 10% to 30%, and the mass ratio of the stabilizer sample to sulfuric acid is 2 to 10: 1 to 5.

6. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S1, the mass ratio of the stabilizer sample to sulfuric acid is 2~10:1~5.

7. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S1, the settling time is 20 to 60 minutes.

8. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S2, slow-speed filter paper is used for filtration, and the drying temperature is 40~80℃.

9. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S3, the washing is performed 1 to 5 times.

10. The method for determining the content of p-tert-butylbenzoic acid and barium in the PVC heat stabilizer as described in claim 1, characterized in that, In step S4, the test conditions for determining the standard and sample using the gas chromatograph are as follows: Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm; Detector: Flame ionization detector; Testing chamber temperature: 300℃; Vaporization chamber temperature: 300℃; Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min; Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0 mL / min; Fuel gas: Hydrogen, purity ≥ 99.999%, flow rate 30 mL / min; Combustion aid: Air, flow rate 400 mL / min.

Images