Method for detecting content of monomethyltin trichloride in methyltin mercaptide compound

Abstract

The invention discloses a method for detecting the content of monomethyltin trichloride in a methyltin mercaptide compound, and belongs to the technical field of component detection. Weighing a methyltin mercaptide compound with the mass of m g, and putting the methyltin mercaptide compound into a titration bottle; dropwise adding methanol into the titration bottle, and shaking until the methyltin mercaptide compound is dissolved; then adding 1ml of an ammonia bromide buffer solution; continuously dropwise adding the iodine-methanol solution until the solution is light yellow and does not fade in 30 seconds, and stopping dropwise adding the iodine-methanol solution; dropwise adding isooctyl thioglycolate into the sample solution, shaking while dropwise adding until the yellow color of the sample solution disappears, and adding a catechol violet indication solution to obtain a test solution; dropwise adding a disodium ethylene diamine tetraacetate standard solution with the concentration of VL being C mol / L into the test solution until the test solution becomes purple red from blue; and calculating an X value according to a formula # imgabs0 #. The method is low in cost, high in accuracy, short in test time and visual and clear in result.

Description

Technical Field

[0001] The invention relates to the technical field of component detection, and in particular to a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound. Background Art

[0002] Methyltin mercaptan compounds are metal organic compounds directly combining tin and carbon. They are mainly used in industrial and agricultural fields such as plastic heat stabilizers, wood preservatives, agricultural pesticides, ship antifouling coatings, and textile mildew inhibitors. With its high efficiency in heat resistance, bactericidal and anti-corrosion properties, it has become one of the most widely used metal organic compounds.

[0003] Methyltin mercaptan heat stabilizer is an important class of fine chemicals and an excellent raw material for preparing heat stabilizers for polyvinyl chloride plastic products. Among them, monomethyltin trichloride has good early processing stability in use, and dimethyltin dichloride has good late processing stability in use. At present, most methyltin mercaptan manufacturers will change the ratio of the two compounds by adjusting the feed amount of tin tetrachloride in production, so as to obtain better processing stability and production benefits. In order to monitor production, the accuracy and timeliness of the detection of monomethyltin trichloride content are particularly critical. At present, there are two methods for detecting monomethyltin trichloride: one is the indirect method, that is, monitoring by detecting monomethyltin trichloride in methyltin chloride aqueous solution, and the other is the direct method, that is, using liquid chromatography external standard method for comparison and detection.

[0004] The two existing detection methods for testing the content of monomethyltin trichloride in methyltin mercaptide compounds have the following problems:

[0005] Indirect method: not only the amount of monomethyl trichloride in the methyltin chloride aqueous solution needs to be titrated, but also its water content needs to be determined by a moisture meter and finally converted to measure. There are cumulative errors in the two detection steps in operation, and the detection accuracy is low and not intuitive.

[0006] Direct method: It is necessary to purchase a monomethyl trichloride reference standard, make parallel samples of the sample and the standard on the chromatogram, and then calculate the average deviation of the peak area for each. The detection is time-consuming, inefficient, and requires high instrument accuracy. Summary of the invention

[0007] The purpose of the present invention is to overcome the above technical deficiencies, provide a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, and solve the technical problems of low detection accuracy, lack of intuitiveness and long time consumption in the prior art for detecting the content of monomethyltin trichloride.

[0008] In order to achieve the above technical purpose, the technical solution of the present invention provides a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, comprising the following steps:

[0009] S1. Weigh mg of methyltin mercaptan compound and put it into a titration bottle;

[0010] S2, adding methanol dropwise to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved; the amount of methanol added is the amount sufficient to dissolve all the methyltin mercaptan;

[0011] S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly;

[0012] S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution;

[0013] S5, adding isooctyl thioglycolate to the sample solution dropwise while shaking until the yellow color of the sample solution disappears, and adding catechol violet indicator solution to obtain a test solution;

[0014] S6, adding a standard solution of disodium ethylenediaminetetraacetate with a VL concentration of C mol / L to the test solution until the test solution changes from blue to purple-red;

[0015] S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound.

[0016] Preferably, the methyltin mercaptan compound in S1 is a mixture of monomethyltin trichloride and dimethyltin dichloride.

[0017] Preferably, the mass concentration of the ammonium bromide buffer solution in S3 is 20%, and it is a water-based solution.

[0018] Preferably, the concentration of the iodine-methanol solution in S4 is 25.38 g / L.

[0019] Preferably, the catechol violet in S5 is a water solution with a concentration of 1-1.2 g / L.

[0020] Preferably, the concentration of the disodium ethylenediaminetetraacetate standard solution in S6 is 0.01-0.1 mol / L. The detection of monomethyltin trichloride in different proportions of methyltin mercaptides can be achieved by changing the concentration of the disodium ethylenediaminetetraacetate standard solution, the sample weight of the object to be measured, and the amount of methanol added to obtain higher accuracy.

[0021] Preferably, the content of monomethyltin trichloride in the methyltin mercaptan compound is 5-9wt%, then m=1, the volume of methanol is 60ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.01mol / L.

[0022] Preferably, the content of monomethyltin trichloride in the methyltin mercaptan compound is 10-19 wt %, then m=1, the volume of methanol is 100 ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.02 mol / L.

[0023] Preferably, the content of monomethyltin trichloride in the methyltin mercaptan compound is 20-30wt%, then m=0.5, the volume of methanol is 100ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.05mol / L.

[0024] Preferably, the content of monomethyltin trichloride in the methyltin mercaptan compound is greater than 30wt%, then m=0.5, the volume of methanol is 100ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.1mol / L.

[0025] In the detection of the present invention, a sample to be tested is dissolved in methanol to form a titration solution, an ammonium bromide buffer solution is added to make the pH value of the titration solution equal to 5.5 (weakly acidic, the pH value of the solution needs to be controlled for complex reaction), and an iodine-methanol solution is added to decompose methyl tin thiol into tetravalent methyl iodotin chloride (tetravalent tin is stable and convenient for titration) under a weakly acidic condition (pH=5.5), wherein the excess iodine is reduced and removed by using isooctyl thioglycolate, and finally during titration, the tetravalent methyl iodotin chloride and disodium ethylenediaminetetraacetate generate a purple-red complex, and catechol violet is used as an indicator.

[0026] Compared with the prior art, the beneficial effects of the present invention include:

[0027] The analysis and detection method used in the present invention can quickly and accurately analyze the component ratio content of monomethyltin trichloride in methyltin mercaptan within 30 minutes. Compared with the indirect method of methyltin chloride aqueous solution which takes 1 hour and the direct chromatography method which takes 3 hours, it is more conducive to the effective and timely monitoring and guidance of continuous and batch production of methyltin mercaptan.

[0028] Moreover, the instruments and reagents used in the present invention are common instruments and conventional reagents, and the detection and analysis costs are low; the waste liquid after the determination is easy to recycle and treat, and the pollution to the environment is small; the determination and analysis steps are simple, the determination and analysis errors are small, and the results are intuitive and clear. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] The relevant information of the substances used in the following examples is as follows:

[0031] The mass concentration of the ammonium bromide buffer solution is 20%, and it is a water-based solution. The concentration of the iodine-methanol solution is 25.38 g / L. The burettes used for titration are calibrated in accordance with GB / T3216-2015. The disodium ethylenediaminetetraacetic acid solution is a standard solution prepared and calibrated in accordance with GB / T601-2006.

[0032] Example 1

[0033] In this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 5.5 wt % is used as a sample to be tested.

[0034] This embodiment provides a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, comprising the following steps:

[0035] S1. Weigh 1 g of a methyltin mercaptan compound and put it into a titration bottle; the methyltin mercaptan compound is a mixture of monomethyltin trichloride and dimethyltin dichloride;

[0036] S2, adding 60 ml of methanol to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved;

[0037] S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly;

[0038] S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution;

[0039] S5, adding isooctyl thioglycolate to the sample solution dropwise while shaking until the yellow color of the sample solution disappears, and adding a 1 g / L aqueous solution of catechol violet indicator to obtain a test solution;

[0040] S6. Add a standard solution of disodium ethylenediaminetetraacetate having a VL concentration of 0.01 mol / L to the test solution until the test solution changes from blue to purple-red;

[0041] S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound;

[0042] S8. Repeat the measurement X 5 times, record them as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0043] Example 2

[0044] This embodiment is the same as the embodiment 1, except that in this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 5.0 wt % is used as a sample to be tested.

[0045] Example 3

[0046] This embodiment is the same as the embodiment 1, except that in this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 9.0 wt % is used as a sample to be tested.

[0047] Example 4

[0048] In this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 13.20 wt % is used as a sample to be tested.

[0049] This embodiment provides a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, comprising the following steps:

[0050] S1. Weigh 1 g of a methyltin mercaptan compound and put it into a titration bottle; the methyltin mercaptan compound is a mixture of monomethyltin trichloride and dimethyltin dichloride;

[0051] S2, adding 100 ml of methanol to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved;

[0052] S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly;

[0053] S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution;

[0054] S5, add isooctyl thioglycolate to the sample solution dropwise, shake while adding dropwise, until the yellow color of the sample solution disappears, add a 1.1 g / L catechol violet indicator aqueous solution to obtain a test solution;

[0055] S6. Add a standard solution of disodium ethylenediaminetetraacetate having a VL concentration of 0.02 mol / L to the test solution until the test solution changes from blue to purple-red;

[0056] S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound;

[0057] S8. Repeat the measurement X 5 times, record them as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0058] Example 5

[0059] This embodiment is the same as embodiment 4, except that in this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 10.0 wt % is used as a test sample.

[0060] Example 6

[0061] This embodiment is the same as embodiment 4, except that in this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 19.0 wt % is used as a test sample.

[0062] Example 7

[0063] In this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 28.50 wt % is used as a sample to be tested.

[0064] This embodiment provides a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, comprising the following steps:

[0065] S1. Weigh 0.5 g of a methyltin mercaptan compound and put it into a titration bottle; the methyltin mercaptan compound is a mixture of monomethyltin trichloride and dimethyltin dichloride;

[0066] S2, adding 100 ml of methanol to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved;

[0067] S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly;

[0068] S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution;

[0069] S5. Add isooctyl thioglycolate dropwise to the sample solution, shaking while adding dropwise until the yellow color of the sample solution disappears, and add a 1.2 g / L catechol violet indicator aqueous solution to obtain a test solution;

[0070] S6. Add a standard solution of disodium ethylenediaminetetraacetate having a VL concentration of 0.05 mol / L to the test solution until the test solution changes from blue to purple-red;

[0071] S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound;

[0072] S8. Repeat the measurement X 5 times, record them as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0073] Example 8

[0074] This example is the same as Example 7, except that in this example, a methyltin mercaptan compound having a monomethyltin trichloride content of 20.0 wt % is used as a test sample.

[0075] Example 9

[0076] This embodiment is the same as embodiment 4, except that in this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 30.0 wt % is used as a sample to be tested.

[0077] Example 10

[0078] In this embodiment, a methyltin mercaptan compound having a monomethyltin trichloride content of 38.40 (more than 30) wt % is used as a test sample.

[0079] This embodiment provides a method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, comprising the following steps:

[0080] S1. Weigh 0.5 g of a methyltin mercaptan compound and put it into a titration bottle; the methyltin mercaptan compound is a mixture of monomethyltin trichloride and dimethyltin dichloride;

[0081] S2, adding 100 ml of methanol to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved;

[0082] S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly;

[0083] S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution;

[0084] S5, adding isooctyl thioglycolate to the sample solution dropwise while shaking until the yellow color of the sample solution disappears, and adding a 1 g / L aqueous solution of catechol violet indicator to obtain a test solution;

[0085] S6. Add a standard solution of disodium ethylenediaminetetraacetate having a VL concentration of 0.1 mol / L to the test solution until the test solution changes from blue to purple-red;

[0086] S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound;

[0087] S8. Repeat the measurement X 5 times, record them as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0088] Comparative Example 1

[0089] The indirect analysis method of methyltin mercaptide chloride aqueous solution was used to determine the test sample with a methyltin trichloride content of 13wt%. Repeat the measurement X 5 times, recorded as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0090] Comparative Example 2

[0091] The indirect analysis method of methyltin mercaptide chloride aqueous solution was used to determine the test sample with a methyltin trichloride content of 28wt%. Repeat the measurement X 5 times, recorded as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0092] Comparative Example 3

[0093] The methyl tin mercaptan compound sample with a content of 30 wt% of monomethyl tin trichloride was determined by direct analysis using chromatographic analysis. Repeat the measurement X 5 times, recorded as X1, X2, X3, X4, X5, and take the average value as X 平均 .

[0094] The measurement results in Examples 1-10 and Comparative Examples 1-3 are shown in Table 1, where X0 refers to the actual content of monomethyltin trichloride in the sample to be tested in this embodiment, and X1, X2, X3, X4, and X5 are the contents of monomethyltin trichloride in the sample to be tested determined by the method of this embodiment, that is, X0 is the actual value, and X1, X2, X3, X4, and X5 are measured values.

[0095] Table 1 Content of monomethyltin trichloride in the test sample As can be seen from the data in the table, the method of the present invention has a smaller relative error and a higher accuracy rate in testing the content of monomethyltin trichloride in the sample to be tested of the mercaptan methyltin compound. In Comparative Example 4 and Comparative Example 1, the content of monomethyltin trichloride in the sample to be tested is about 13wt%, and the relative error is 1.29% when measured by the method in Example 4, and 2.08% when measured by the test method in the prior art. For the sample to be tested with a higher content of monomethyltin trichloride, the accuracy of the method of the present invention is higher than that of the measurement method in the prior art, and the error is smaller.

[0096] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for detecting the content of monomethyltin trichloride in a methyltin mercaptan compound, characterized in that: The following steps are involved: S1. Weigh mg of methyltin mercaptan compound and put it into a titration bottle; S2, adding methanol dropwise to the titration bottle, and shaking until the methyltin mercaptan compound is dissolved; S3, add 1 ml of ammonium bromide buffer solution and shake until mixed evenly; S4, continue to drop the iodine-methanol solution until the solution turns light yellow and does not fade for 30 seconds, stop dropping the iodine-methanol solution, and obtain a sample solution; S5, adding 99% pure isooctyl thioglycolate to the sample solution, shaking while adding, until the yellow color of the sample solution disappears, adding catechol violet indicator solution, and obtaining a test solution; S6, adding a standard solution of disodium ethylenediaminetetraacetate with a VL concentration of C mol / L to the test solution until the test solution changes from blue to purple-red; S7, according to the formula Calculate the X value, wherein X is the content of monomethyltin trichloride in the methyltin mercaptan compound.

2. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 1, characterized in that: The methyltin mercaptan compound in S1 is a mixture of monomethyltin trichloride and dimethyltin dichloride.

3. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 1, characterized in that: The mass concentration of the ammonium bromide buffer solution in S3 is 20%.

4. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 1, characterized in that: The concentration of the iodine-methanol solution in S4 is 25.38 g / L.

5. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 1, characterized in that: The catechol violet in S5 is a water solution with a concentration of 1-1.2 g / L.

6. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 1, characterized in that: The concentration of the disodium ethylenediaminetetraacetic acid standard solution described in S6 is 0.01-0.1 mol / L.

7. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 6, characterized in that: The content of monomethyltin trichloride in the methyltin mercaptan compound is 5-9wt%, then m=1, the volume of methanol is 60ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.01mol / L.

8. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 6, characterized in that: The content of monomethyltin trichloride in the methyltin mercaptan compound is 10-19 wt %, then m=1, the volume of methanol is 100 ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.02 mol / L.

9. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 6, characterized in that: The content of monomethyltin trichloride in the methyltin mercaptan compound is 20-30wt%, then m=0.5, the volume of methanol is 100ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.05mol / L.

10. The method for detecting the content of monomethyltin trichloride in the methyltin mercaptan compound according to claim 6, characterized in that: The content of monomethyltin trichloride in the methyltin mercaptan compound is greater than 30 wt %, then m=0.5, the volume of methanol is 100 ml, and the concentration of the disodium ethylenediaminetetraacetic acid standard solution is 0.1 mol / L.

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