A dissolution precipitation-gas chromatography method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate

Abstract

The present invention relates to a dissolution precipitation-gas chromatography method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate, comprising the following steps: (1) a dissolution precipitation preparation method for a sample solution; (2) preparation of an organic mixed solution; (3) preparation of a standard series of solutions of dichloromethane, chloroform and carbon tetrachloride; (4) drawing of a standard curve of the content of dichloromethane, chloroform and carbon tetrachloride; (5) determination of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate; (6) calculation of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate. The method of the present invention has the advantages of simple operation, rapidity, good repeatability and high accuracy, and is suitable for the determination of the residual content of dichloromethane, chloroform and carbon tetrachloride in similar substances.

Description

Technical Field

[0001] The invention belongs to the field of chemical analysis, and in particular relates to a dissolution precipitation-gas chromatography method for determining the contents of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate. Background Art

[0002] Polycarbonate (PC for short) is a high molecular polymer containing carbonate groups in the molecular chain. Due to the special structure of polycarbonate, polycarbonate has become the fastest growing general engineering plastic among the five major engineering plastics, and its application field is very wide. When producing polycarbonate by phosgene method, dichloromethane is used as solvent. Since dichloromethane contains impurities such as chloroform and carbon tetrachloride, chloroform and carbon tetrachloride will be carried in the system, resulting in residual dichloromethane solvent, chloroform impurities and carbon tetrachloride impurities in the product polycarbonate. These residual organic substances will affect the quality of the product and the quality of downstream products. Therefore, it is necessary to control the content of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate. The journals "Determination of Dichloromethane in Polycarbonate by Gas Chromatography" and "Determination of Residual Dichloromethane in PC by Multiple Headspace Extraction-Gas Chromatography" disclose methods for detecting the residual dichloromethane content in polycarbonate, but a method for simultaneously detecting the residual dichloromethane, chloroform and carbon tetrachloride contents in polycarbonate has not been reported. The present invention adopts dissolution precipitation-gas chromatography for the first time to detect the residual dichloromethane, chloroform and carbon tetrachloride contents in polycarbonate. Summary of the invention

[0003] In order to solve the above-mentioned shortcomings of the background technology, the purpose of the present invention is to overcome the technical deficiencies and provide a method for determining the content of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate which is simple to operate, rapid and highly accurate.

[0004] A method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate comprises the following steps:

[0005] (1) Prepare sample solution by dissolution precipitation method: accurately weigh 0.2-0.6g of polycarbonate sample to an accuracy of 0.0001g, add an appropriate amount of organic solvent to a 20mL reagent bottle, and accurately weigh the mass of the organic solvent to an accuracy of 0.01g, shake on an oscillator until completely dissolved, slowly add an appropriate amount of organic precipitant, and accurately weigh the mass of the organic precipitant to an accuracy of 0.01g, shake on an oscillator for 10 min to 30 min, and make a blank at the same time;

[0006] (2) Preparation of organic mixed solution: Select appropriate organic solvents and proportions to mix two or three organic mixed solutions evenly;

[0007] (3) Prepare high-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride with organic mixed solvents: Use organic mixed solution as solvent to prepare standard series solutions. For the preparation of standard solution #1, accurately weigh the organic mixed solution, dichloromethane, chloroform and carbon tetrachloride to 103.7282 g, 0.0038 g, 0.0031 g and 0.0037 g, respectively. For the preparation of standard solution #2, accurately weigh the organic mixed solution, dichloromethane, chloroform and carbon tetrachloride to 103.7282 g, 0.0038 g, 0.0031 g and 0.0037 g, respectively. 6g, 0.0080g, 0.0070g, 0.0067g; for the preparation of 3# standard solution, the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride were accurately weighed to be 103.7391g, 0.0130g, 0.0099g, and 0.0101g, respectively; for the preparation of 4# standard solution, the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride were accurately weighed to be 103.7214g, 0.0177g, 0.0137g, and 0.0134g, respectively;

[0008] (4) Preparation of low-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride using organic mixed solvents: Use organic mixed solvents as solvents to prepare standard series solutions. Standard solutions #5 and #6 are obtained by diluting standard solution #1 by 100 times and 20 times, and standard solutions #7, #8 and #9 are obtained by diluting standard solution #2 by 20 times, 10 times and 5 times;

[0009] (5) Drawing of standard curve: Use gas chromatograph-ECD with automatic sampler to measure the peak areas of dichloromethane, chloroform and carbon tetrachloride standard series solutions respectively, and draw the curve with the content of dichloromethane, chloroform and carbon tetrachloride in the standard series solutions as the ordinate and the peak area as the abscissa;

[0010] (6) Determination of residual dichloromethane, chloroform and carbon tetrachloride content in polycarbonate samples:

[0011] ① Determination of blank solution: Use gas chromatograph-ECD with automatic sample injector to determine the content of dichloromethane, chloroform and carbon tetrachloride in blank solution. 01 , C 02 , C 03 .

[0012] ② Use gas chromatograph-ECD with automatic sampler to measure the peak area of ​​dichloromethane, chloroform and carbon tetrachloride standard solution in the sample. The instrument automatically gives the contents of dichloromethane, chloroform and carbon tetrachloride C1, C2 and C3 in the sample solution.

[0013] (6) Calculation of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples: The residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples is calculated according to the formulax 1=(C1- C 01 )×(m1+m2) / m0, x 2 = (C2-C 02 )×(m1+m2) / m0, x 3=(C3- C 03 )×(m1+m2) / m0, where x 1 represents the residual methylene chloride content in the polycarbonate sample, x 2 represents the residual chloroform content in the polycarbonate sample, x 3 represents the residual carbon tetrachloride content in the polycarbonate sample, C1 represents the content of dichloromethane in the prepared sample solution, C2 represents the content of chloroform in the prepared sample solution, C3 represents the content of carbon tetrachloride in the prepared sample solution, and C 01 Indicates the content of dichloromethane in the blank solution, C 02 Indicates the content of chloroform in the blank solution, C 03 represents the content of carbon tetrachloride in the blank solution, m1 represents the mass of the appropriate amount of organic solvent, m2 represents the mass of the appropriate amount of organic precipitant, and m0 represents the mass of the weighed polycarbonate.

[0014] Preferably, in the steps (2), (3) and (4), the organic mixed solution is a mixture of two or three solvents, one or two of which are selected from tetrahydrofuran, acetonitrile or benzene; and the other one or two are selected from benzyl alcohol, methanol or acetone. More preferably, when the organic mixed solution is two mixed solutions, the ratio of the organic mixed solution is 1:1, 1:2, 1:3, 1:4, 1:5, preferably 1:1.

[0015] Preferably, in step (1), the organic solvent added is tetrahydrofuran, acetonitrile, benzene or acetone, preferably tetrahydrofuran, and the amount added is 5 mL to 15 mL.

[0016] Preferably, in step (1), the organic precipitant added is methanol, ethanol or propanol, preferably methanol, and the amount added is 5 mL to 15 mL.

[0017] In step (5) of the method of the present application, the gas chromatography conditions are: the stationary phase of the chromatographic column is 6% cyanopropylbenzene and 94% dimethylsiloxane, 100% polysiloxane, 5% phenyl and 95% polysiloxane, preferably 6% cyanopropylbenzene and 94% dimethylsiloxane; the long-diameter membrane thickness of the chromatographic column is 60m×0.25mm×1.4μm, 60m×0.32mm×1.4μm, 30m×0.25mm×1.4μm, preferably 60m×0.25mm×1.4μm; the carrier gas flow rate is 1 mL / min~2mL / min; the initial column temperature is 30℃~40℃, maintained for 10min~20min, and the temperature is programmed to rise by 5℃ / min~20℃ / min, raised to 230℃, and maintained for 10 min~20min.

[0018] The invention has the following beneficial effects: the invention provides a method for determining the content of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate. The method first dissolves the sample in an organic solvent, then adds an organic precipitant, and utilizes the characteristics of polycarbonate being insoluble in the organic precipitant and dichloromethane, chloroform and carbon tetrachloride solution as organic precipitants to precipitate polycarbonate from the sample solution, thereby eliminating the influence of polycarbonate on the detection and the damage to the chromatographic column. The method adopts an organic mixed solution as a solvent to prepare a standard solution. The organic mixed solution has a higher boiling point than a single organic solvent, and can reduce The error caused by low solvent volatilization is improved, and the accuracy of standard solution preparation is improved. The present invention adopts gas chromatography-ECD equipped with an automatic sampler to detect the content of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate. The ECD detector has high sensitivity and can detect the content of trace dichloromethane, chloroform and carbon tetrachloride in polycarbonate. The automatic sampler can realize accurate sampling, improve the accuracy and repeatability of detection. The method described in the present invention has the advantages of high accuracy, good repeatability, simple operation and the like, and is suitable for the determination of the content of dichloromethane, chloroform and carbon tetrachloride in similar substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Standard curve of dichloromethane content;

[0020] Figure 2 Standard curve of chloroform content;

[0021] Figure 3 Standard curve of carbon tetrachloride content;

[0022] Figure 4 Standard curve of single solvent dichloromethane content;

[0023] Figure 5 Standard curve of chloroform content of a single solvent;

[0024] Figure 6 Standard curve of carbon tetrachloride content in a single solvent. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention and to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is further described in detail below in conjunction with embodiments.

[0026] Example 1

[0027] (1) Preparation of sample solution: Accurately weigh 0.3 g of polycarbonate pellets to an accuracy of 0.0001 g, place in a 20 mL reagent bottle, add 10 mL of tetrahydrofuran, and accurately weigh the mass of tetrahydrofuran to an accuracy of 0.01 g, shake on an oscillator until completely dissolved, slowly add 5 mL of methanol, and accurately weigh the mass of methanol to an accuracy of 0.01 g, shake on an oscillator for 20 min, prepare 6 parallel sample solutions, and prepare a blank solution at the same time;

[0028] (2) Preparation of organic mixed solution: Select appropriate organic solvents and proportions to mix two or three organic mixed solutions evenly;

[0029] (3) Preparation of high-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride using organic mixed solution: Use benzyl alcohol-tetrahydrofuran mixed solution as solvent to prepare standard series solutions. For the preparation of standard solution #1, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform and carbon tetrachloride to a mass of 103.7282 g, 0.0038 g, 0.0031 g and 0.0037 g, respectively; for the preparation of standard solution #2, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform and carbon tetrachloride to a mass of 103. 7286g, 0.0080g, 0.0070g, 0.0067g; 3# standard solution preparation, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform, carbon tetrachloride mass 103.7391g, 0.0130g, 0.0099g, 0.0101g; 4# standard solution preparation, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform, carbon tetrachloride mass 103.7214g, 0.0177g, 0.0137g, 0.0134g;

[0030] (4) Preparation of low-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride using organic mixed solutions: Use benzyl alcohol-tetrahydrofuran mixed solution as solvent to prepare standard series solutions. Standard solutions 5# and 6# are obtained by diluting standard solution 1# by 100 times and 20 times respectively. Standard solutions 7#, 8# and 9# are obtained by diluting standard solution 2# by 20 times, 10 times and 5 times respectively.

[0031] (5) Drawing of standard curve: Use gas chromatograph-ECD with automatic sampler to measure the peak area of ​​dichloromethane, chloroform and carbon tetrachloride standard series solutions respectively, and draw the curve with the content of dichloromethane, chloroform and carbon tetrachloride in the standard series solutions as the ordinate and the peak area as the abscissa. The gas chromatography conditions are: chromatographic column stationary phase 6% cyanopropylbenzene and 94% dimethylsiloxane, chromatographic column length × diameter × film thickness 60m × 0.25mm × 1.4μm, carrier gas flow rate 1.5mL / min, split ratio 10:1, injection port temperature 230℃, detector temperature 300℃, tail gas flow rate 60mL / min, initial column temperature 32℃ maintained for 17min, increased to 230℃ at 10℃ / min and maintained for 10min.

[0032] (6) Repeatability determination of residual dichloromethane, chloroform and carbon tetrachloride content in polycarbonate samples:

[0033] ① Determination of blank solution: Use gas chromatograph-ECD with automatic sample injector to determine the content of dichloromethane, chloroform and carbon tetrachloride in blank solution. 01 , C 02 , C 03 .

[0034] ② Use gas chromatograph-ECD with automatic sampler to measure the peak area of ​​dichloromethane, chloroform and carbon tetrachloride standard solution in the sample. The instrument automatically gives the contents of dichloromethane, chloroform and carbon tetrachloride C1, C2 and C3 in the sample solution.

[0035] (7) Calculation of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples: The residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples is calculated according to the formula x 1=(C1- C 01 )×(m1+m2) / m0, x 2 = (C2-C 02 )×(m1+m2) / m0, x 3=(C3- C 03 )×(m1+m2) / m0, where x 1 represents the residual methylene chloride content in the polycarbonate sample, x 2 represents the residual chloroform content in the polycarbonate sample, x 3 represents the residual carbon tetrachloride content in the polycarbonate sample, C1 represents the content of dichloromethane in the prepared sample solution, C2 represents the content of chloroform in the prepared sample solution, C3 represents the content of carbon tetrachloride in the prepared sample solution, and C 01 Indicates the content of dichloromethane in the blank solution, C 02 Indicates the content of chloroform in the blank solution, C03 represents the content of carbon tetrachloride in the blank solution, m1 represents the mass of tetrahydrofuran, m2 represents the mass of methanol, and m0 represents the mass of the weighed polycarbonate. x 1=(C1- C 01 )×(m1+m2) / m0, x 2 = (C2-C 02 )×(m1+m2) / m0, x 3=(C3- C 03 )×(m1+m2) / m0In order to facilitate calculation, the units of various parameters are optimized, among which C 01 , C 02 , C 03 、C1、C2、C3、 x 1. x 2. x The unit of 3 is μg / g, and the unit of m1, m2, and m0 is g. The obtained values ​​are shown in Tables 1, 2, and 3.

[0036] Table 1 Repeatability of residual dichloromethane content detection in pelletized polycarbonate

[0037]

[0038] Table 2 Repeatability of residual chloroform content detection in pelletized polycarbonate

[0039]

[0040] Table 3 Repeatability of detection of residual carbon tetrachloride content in pelletized polycarbonate

[0041]

[0042] (6) Determination of the recovery rate of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples:

[0043] Under the selected working conditions, a spike test was carried out, and the test results are shown in Tables 4, 5 and 6. It can be seen from the results of Tables 4, 5 and 6 that the recovery rate of dichloromethane spiked is between 98.84% and 104.61%, which meets the test requirements, the recovery rate of chloroform spiked is between 98.48% and 104.27%, which meets the test requirements, and the recovery rate of carbon tetrachloride spiked is between 97.11% and 104.17%, which meets the test requirements.

[0044] Table 4 Residual dichloromethane spike recovery in pelletized polycarbonate

[0045]

[0046] Table 5 Residual chloroform spiked recovery in pelletized polycarbonate

[0047]

[0048] Table 6 Residual carbon tetrachloride spiked recovery in pelletized polycarbonate

[0049]

[0050] Example 2

[0051] (1) Preparation of sample solution: Accurately weigh 0.3 g of polycarbonate flakes to an accuracy of 0.0001 g, place in a 20 mL reagent bottle, add 10 mL of tetrahydrofuran, and accurately weigh the mass of tetrahydrofuran to an accuracy of 0.01 g, shake on an oscillator until completely dissolved, slowly add 5 mL of methanol, and accurately weigh the mass of methanol to an accuracy of 0.01 g, shake on an oscillator for 20 min, prepare 6 parallel sample solutions, and prepare a blank solution at the same time;

[0052] (2) Preparation of organic mixed solution: Select appropriate organic solvents and proportions to mix two or three organic mixed solutions evenly;

[0053] (3) Preparation of high-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride using organic mixed solution: Use benzyl alcohol-tetrahydrofuran mixed solution as solvent to prepare standard series solutions. For the preparation of standard solution #1, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform and carbon tetrachloride to a mass of 103.7282 g, 0.0038 g, 0.0031 g and 0.0037 g, respectively; for the preparation of standard solution #2, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform and carbon tetrachloride to a mass of 103. 7286g, 0.0080g, 0.0070g, 0.0067g; 3# standard solution preparation, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform, carbon tetrachloride mass 103.7391g, 0.0130g, 0.0099g, 0.0101g; 4# standard solution preparation, accurately weigh the benzyl alcohol-tetrahydrofuran mixed solution, dichloromethane, chloroform, carbon tetrachloride mass 103.7214g, 0.0177g, 0.0137g, 0.0134g;

[0054] (4) Preparation of low-concentration standard series solutions of dichloromethane, chloroform and carbon tetrachloride using organic mixed solutions: Use benzyl alcohol-tetrahydrofuran mixed solution as solvent to prepare standard series solutions. Standard solutions 5# and 6# are obtained by diluting standard solution 1# by 100 times and 20 times respectively. Standard solutions 7#, 8# and 9# are obtained by diluting standard solution 2# by 20 times, 10 times and 5 times respectively.

[0055] (5) Preparation of standard curve: The peak areas of the standard series solutions of dichloromethane, chloroform and carbon tetrachloride were measured by gas chromatograph-ECD with automatic sampler, and the curve was plotted with the contents of dichloromethane, chloroform and carbon tetrachloride in the standard series solutions as the ordinate and the peak areas as the abscissa. The gas chromatography conditions were as follows: the stationary phase of the chromatographic column was 6% cyanopropylbenzene and 94% dimethylsiloxane, the length × diameter × film thickness of the chromatographic column was 60 m × 0.25 mm × 1.4 μm, the carrier gas flow rate was 1.5 mL / min, the split ratio was 10:1, the injection port temperature was 230 °C, the detector temperature was 300 °C, the tail gas flow rate was 60 mL / min, the initial column temperature was 32 °C and maintained for 17 min, then increased to 230 °C at a rate of 10 °C / min and maintained for 10 min.

[0056] (6) Repeatability determination of residual dichloromethane, chloroform and carbon tetrachloride content in polycarbonate samples:

[0057] ① Determination of blank solution: Use gas chromatograph-ECD with automatic sample injector to determine the content of dichloromethane, chloroform and carbon tetrachloride in blank solution. 01 , C 02 , C 03 .

[0058] ② Use gas chromatograph-ECD with automatic sampler to measure the peak area of ​​dichloromethane, chloroform and carbon tetrachloride standard solution in the sample. The instrument automatically gives the contents of dichloromethane, chloroform and carbon tetrachloride C1, C2 and C3 in the sample solution.

[0059] (7) Calculation of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples: The residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples is calculated according to the formula x 1=(C1- C 01 )×(m1+m2) / m0, x 2 = (C2-C 02 )×(m1+m2) / m0, x 3=(C3- C 03 )×(m1+m2) / m0, where x 1 represents the residual methylene chloride content in the polycarbonate sample, x 2 represents the residual chloroform content in the polycarbonate sample, x 3 represents the residual carbon tetrachloride content in the polycarbonate sample, C1 represents the content of dichloromethane in the prepared sample solution, C2 represents the content of chloroform in the prepared sample solution, C3 represents the content of carbon tetrachloride in the prepared sample solution, and C 01 Indicates the content of dichloromethane in the blank solution, C 02 Indicates the content of chloroform in the blank solution, C03 represents the content of carbon tetrachloride in the blank solution, m1 represents the mass of tetrahydrofuran, m2 represents the mass of alcohol, and m0 represents the mass of the weighed polycarbonate. x 1=(C1- C 01 )×(m1+m2) / m0, x 2 = (C2-C 02 )×(m1+m2) / m0, x 3=(C3- C 03 )×(m1+m2) / m0In order to facilitate calculation, the units of various parameters are optimized, among which C 01 , C 02 , C 03 、C1、C2、C3、 x 1. x 2. x The unit of 3 is μg / g, and the unit of m1, m2, and m0 is g. The obtained values ​​are shown in Table 1, Table 2, and Table 3. The obtained values ​​are shown in Table 7, Table 8, and Table 9.

[0060] Table 7 Repeatability of residual dichloromethane content detection in polycarbonate flakes

[0061]

[0062] Table 8 Repeatability of residual chloroform content detection in polycarbonate sheets

[0063]

[0064] Table 9 Repeatability of detection of residual carbon tetrachloride content in polycarbonate flakes

[0065]

[0066] (6) Determination of the recovery rate of residual dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples:

[0067] Under the selected working conditions, a spike test was carried out, and the test results are shown in Tables 10, 11 and 12. It can be seen from the results in Tables 10, 11 and 12 that the recovery rate of dichloromethane spiked is between 98.24% and 103.97%, which meets the test requirements, the recovery rate of chloroform spiked is between 97.38% and 104.87%, which meets the test requirements, and the recovery rate of carbon tetrachloride spiked is between 98.03% and 104.35%, which meets the test requirements.

[0068] Table 10 Residual dichloromethane spike recovery in polycarbonate flakes

[0069]

[0070] Table 11 Residual chloroform spiked recovery in polycarbonate flakes

[0071]

[0072] Table 12 Residual carbon tetrachloride spiked recovery in polycarbonate flakes

[0073]

[0074] During the experiment, we also used a single solvent for testing, but the effect was poor. The following is a comparison of the standard curves of a single solvent and a mixed solvent:

[0075] (1) Selection of a single solvent: Select a single solvent that can quickly dissolve polycarbonate. Tetrahydrofuran is the best choice. Other solvents dissolve slowly or cannot dissolve it.

[0076] (3) Preparation of a series of standard solutions of dichloromethane, chloroform and carbon tetrachloride using a single solvent: Use tetrahydrofuran as the solvent to prepare a series of standard solutions. For the preparation of standard solution #1, accurately weigh tetrahydrofuran, dichloromethane, chloroform and carbon tetrachloride to a mass of 102.3422 g, 0.0176 g, 0.0132 g and 0.0131 g, respectively. For the preparation of standard solution #2, accurately weigh tetrahydrofuran, dichloromethane, chloroform and carbon tetrachloride to a mass of 102.3522 g, 0.0124 g, 0.0096 g and 0.0090 g, respectively. For standard solution #3, accurately weigh tetrahydrofuran, dichloromethane, chloroform and carbon tetrachloride to a mass of 102.3522 g, 0.0124 g, 0.0096 g and 0.0090 g, respectively. Preparation of 1# standard solution, accurately weighing 102.3428g, 0.0081g, 0.0067g, 0.0030g of tetrahydrofuran, dichloromethane, chloroform, and carbon tetrachloride; Preparation of 4# standard solution, accurately weighing 102.3501g, 0.0036g, 0.0030g, 0.0034g of tetrahydrofuran, dichloromethane, chloroform, and carbon tetrachloride; Standard solutions 5#, 6#, and 7# were prepared by diluting standard solution 3# by 5, 10, and 20 times, and solutions 4# and 9# were prepared by diluting standard solution 1# by 100 and 20 times;

[0077] (4) Preparation of standard curve: The peak areas of the standard series solutions of dichloromethane, chloroform and carbon tetrachloride were measured by gas chromatograph-ECD with automatic sampler, and the curve was plotted with the contents of dichloromethane, chloroform and carbon tetrachloride in the standard series solutions as the ordinate and the peak areas as the abscissa. The gas chromatography conditions were as follows: the stationary phase of the chromatographic column was 6% cyanopropylbenzene and 94% dimethylsiloxane, the length × diameter × film thickness of the chromatographic column was 60 m × 0.25 mm × 1.4 μm, the carrier gas flow rate was 1.5 mL / min, the split ratio was 10:1, the injection port temperature was 230 °C, the detector temperature was 300 °C, the tail gas flow rate was 60 mL / min, the initial column temperature was 32 °C and maintained for 17 min, then increased to 230 °C at a rate of 10 °C / min and maintained for 10 min.

[0078] (5) The linear relationship of the standard solution prepared with a single solvent, such as Figure 4 ,like Figure 5 , Figure 6 Show.

[0079] (6) The experimental results show that the linearity of the mixed solvent standard curve is higher than that of the single solvent standard solution curve.

Claims

1. A dissolution precipitation-gas chromatography method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate, characterized in that: The following steps are involved: (1) Prepare sample solution by dissolution-precipitation method: accurately weigh 0.3 g of polycarbonate sample to 0.0001 g, add 10 mL of tetrahydrofuran to a 20 mL reagent bottle, and accurately weigh the mass of tetrahydrofuran to 0.01 g, shake on an oscillator until completely dissolved, slowly add 5 mL of methanol, and accurately weigh the mass of methanol to 0.01 g, shake on an oscillator for 10 min to 30 min, and prepare a blank solution at the same time; (2) Preparation of organic mixed solution: Select appropriate organic solvents and proportions to mix two or three organic solvents evenly; (3) Organic mixed solution to prepare high concentration dichloromethane, chloroform, carbon tetrachloride standard series solutions: Use organic mixed solution as solvent to prepare standard series solutions. For the preparation of 1# standard solution, accurately weigh the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride to a mass of 103.7282 g, 0.0038 g, 0.0031 g, and 0.0037 g, respectively, and mix them evenly. For the preparation of 2# standard solution, accurately weigh the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride to a mass of 103.7286 g, 0.0038 g, 0.0031 g, and 0.0037 g, respectively, and mix them evenly. .0080g, 0.0070g, 0.0067g and mix evenly; for the preparation of 3# standard solution, accurately weigh the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride to be 103.7391g, 0.0130g, 0.0099g, and 0.0101g respectively and mix evenly; for the preparation of 4# standard solution, accurately weigh the organic mixed solution, dichloromethane, chloroform, and carbon tetrachloride to be 103.7214g, 0.0177g, 0.0137g, and 0.0134g respectively and mix evenly; (4) Preparation of standard series solutions of low dichloromethane, chloroform and carbon tetrachloride using organic mixed solution: Use organic mixed solution as solvent to prepare standard series solutions. Standard solutions 5# and 6# are obtained by diluting standard solution 1# by 100 times and 20 times respectively. Standard solutions 7#, 8# and 9# are obtained by diluting standard solution 2# by 20 times, 10 times and 5 times respectively. (5) Drawing of standard curve: Use gas chromatograph-ECD with automatic sample injector to measure, select appropriate gas chromatographic conditions to measure the peak areas of dichloromethane, chloroform and carbon tetrachloride standard series solutions respectively, and draw the curve with the content of dichloromethane, chloroform and carbon tetrachloride in the standard series solutions as the ordinate and the peak area as the abscissa; (6) Determination of residual dichloromethane, chloroform and carbon tetrachloride content in polycarbonate samples: ① Determination of blank solution: Use gas chromatograph-ECD with automatic sample injector to determine the content of dichloromethane, chloroform and carbon tetrachloride in blank solution. 01 , C 02 , C 03 ; ②Use gas chromatograph-ECD with automatic sample injector to measure the peak area of ​​dichloromethane, chloroform and carbon tetrachloride standard solution in the sample. The instrument automatically gives the contents of dichloromethane, chloroform and carbon tetrachloride C1, C2 and C3 in the sample solution; (7) Calculation of the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples: The residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate samples is calculated according to the formula x1 = (C1-C 01 ) × (m1+ m2) / m0, x2= (C2-C 02 ) × (m1+ m2) / m0, x3= (C3- C 03 )×(m1+ m2) / m0, where x1 represents the residual dichloromethane content in the polycarbonate sample, x2 represents the residual chloroform content in the polycarbonate sample, x3 represents the residual carbon tetrachloride content in the polycarbonate sample, C1 represents the content of dichloromethane in the prepared sample solution, C2 represents the content of chloroform in the prepared sample solution, C3 represents the content of carbon tetrachloride in the prepared sample solution, and C 01 Indicates the content of dichloromethane in the blank solution, C 02 Indicates the content of chloroform in the blank solution, C 03 represents the content of carbon tetrachloride in the blank solution, m1 represents the mass of the appropriate amount of organic solvent, m2 represents the mass of the appropriate amount of organic precipitant, and m0 represents the mass of the weighed polycarbonate; the above formula 1 = (C1- C 01 ) × (m1+ m2) / m0, x2= (C2- C 02 ) × (m1+ m2) / m0, x3= (C3- C 03 )×(m1+ m2) / m0In order to facilitate calculation, the units of each parameter are optimized, among which C 01 , C 02 , C 03 The unit of C1, C2, C3, x1, x2, x3 is μg / g, and the unit of m1, m2, m0 is g.

2. The method of dissolution precipitation-gas chromatography for determining the residual methylene chloride, chloroform and carbon tetrachloride in polycarbonate according to claim 1, characterized in that: In steps (2), (3) and (4), the organic mixed solution is a mixture of two or three solvents, one or two of which are selected from tetrahydrofuran, acetonitrile or benzene; and the other one or two are selected from benzyl alcohol, methanol or acetone.

3. The method of dissolution precipitation-gas chromatography for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate according to claim 1, characterized in that: In the steps (2), (3) and (4), when the organic mixed solution is two mixed solutions, the ratio of the organic mixed solution is 1:1, 1:2, 1:3, 1:4 or 1:

5.

4. A dissolution precipitation-gas chromatography method for determining the residual methylene chloride, chloroform and carbon tetrachloride content in polycarbonate as claimed in claim 3, characterized in that: In the steps (2), (3) and (4), when the organic mixed solution is two mixed solutions, the ratio of the organic mixed solutions is 1:

1.

5. A dissolution precipitation-gas chromatography method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate as claimed in claim 1, characterized in that: In the step (5), the gas chromatography conditions are as follows: the stationary phase of the chromatographic column is 6% cyanopropylbenzene and 94% dimethylsiloxane, 100% polysiloxane, 5% phenyl and 95% polysiloxane; the long-diameter membrane thickness of the chromatographic column is 60m×0.25mm×1.4μm, 60m×0.32mm×1.4μm, and 30m×0.25mm×1.4μm; the carrier gas flow rate is 1 mL / min to 2mL / min; the initial column temperature is 30°C to 40°C, maintained for 10 min to 20 min, and the temperature is programmed to rise by 5°C / min to 20°C / min, raised to 230°C, and maintained for 10 min to 20 min.

6. A dissolution precipitation-gas chromatography method for determining the residual content of dichloromethane, chloroform and carbon tetrachloride in polycarbonate as claimed in claim 5, characterized in that: In the step (5), the gas chromatography conditions are as follows: the stationary phase of the chromatographic column is 6% cyanopropylbenzene and 94% dimethylsiloxane; the thickness of the long-aperture membrane of the chromatographic column is 60m×0.25mm×1.4μm.

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