Calculation of the methanol mass fraction in pure methanol
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According to Appendix B of the national standard GB338-2011, the mass fraction of methanol in pure methanol can be calculated. So what I want to ask is. How is the methanol mass fraction in methanol of premium grade as per national standards calculated? What analysis methods are available? Are there any new changes or requirements in the national standards? I would appreciate guidance from those with more experience!
The impurities in pure methanol are relatively low, making it difficult to determine its purity directly, as its other physical properties are identical to those of pure methanol. In such cases, accurate analysis of the residual impurities in methanol should be carried out using chromatography, and then the mass fraction of methanol should be calculated through subtraction. For impurity analysis, the correction method can use mass units. The impurities in refined methanol are mainly high-boiling-point fusel oils and water; however, water needs to be analyzed separately, as chromatographic analysis for trace amounts of water is not suitable. The Karl Fischer titration method can be used for this purpose.