Trimellitic anhydride for industrial use (2)

4 Test method

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Some test procedures specified in the test method may lead to dangerous situations, and the operator should take appropriate safety and protective measures

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Unless otherwise specified, only reagents confirmed to be analytically pure and grade 3 water that meets the requirements of GB/T6682-2008 are used in the analysis

The standard titration solutions, preparations and products used in the analysis shall be prepared in accordance with the provisions of GB/T601-2002 and GB/T603-2002 when other requirements are not specified

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Add laboratory samples to the Juzhai colorimetric tube and visually inspect it under fluorescent light or sunlight

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The impurity components such as trimellitic anhydride, pyromellitic dianhydride, trimellitic acid , terephthalic acid and isophthalic acid in laboratory samples are dissolved in water and converted into corresponding acids

When the mass fraction of trimellitic acid is greater than or equal to 95%, the mass fraction of trimellitic acid in the sample is used to approximate the mass fraction of trimellitic anhydride in laboratory samples, and the relative deviation does not exceed 0.

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2 Recorder: chromatographic data workstation or chromatographic data processor
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3 Micro-injector: 5uL or suitable capacity
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4 Chromatographic column and typical chromatographic operating conditions

The recommended chromatographic column and typical operating conditions are shown in Table 2, the typical high performance liquid chromatogram is shown in Appendix A, Figure A.
1, and the retention time of each component is shown in Appendix A, Table A.
1
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Other chromatographic columns and chromatographic operating conditions that can achieve the same degree of separation can be used
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Table 2 Chromatographic column and typical chromatographic operating conditions

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5 Analysis steps

Weigh 0.
1g of laboratory sample, accurate to 0.
0001g, place it in a 250mL conical flask or beaker, add 20ml of water, transfer it into a water bath at (70±5)℃ and heat for about 20min, shake to dissolve the sample, and add to the flow Dilute the solution to an appropriate concentration, so that the measured component chromatographic peaks have an appropriate height
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The sample is drawn with a micro-injector and injected into the liquid chromatograph for measurement
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6 Quantitative methods

Corrected area normalization method
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Refer to Appendix B for the determination of relative mass correction factors
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7 Result calculation

The mass fraction w _{i of} trimellitic acid and other components in the sample , expressed in %, are calculated according to formula (1):

Where:

f _i — the relative mass correction factor of the measured component i;

A _i —the peak area of ​​the measured component i;

∑f _i A _i — the sum of the corrected peak areas of each component
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Divide the mass fraction of each component in the sample by the molecular weight of the corresponding component to obtain the mole fraction of the corresponding component
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According to the change of the mole fraction of each component before and after the hydrolysis of the sample, the mole fraction of each component in the laboratory sample can be obtained, and then the mass fraction of the corresponding component can be converted according to the molecular weight of each component in the laboratory sample
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For some unknown impurities with small mass fractions in the sample, their mass fractions can be approximated to their mass fractions in laboratory samples
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Regarding the content of trimellitic anhydride , the absolute difference between the two independent test results obtained under repeatability conditions is not more than 0.
02%, assuming that it is not more than 5% if it is greater than 0.
02%
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