GB/T 35952-2018 in English

Standard working solution treatment:Take the standard solution of undecylenic acid at various concentrations, add sulfuric acid methanol solution, and react in a $65~^{\circ}C$ water bath for $1~\mathrm{h}$. After cooling, add n-hexane, vortex mix and add saturated sodium chloride solution. After standing and stratification, wash the organic layer, take the upper organic layer, filter and inject.

Sample treatment:Accurately weigh $0.25\mathrm{~g}$ sample, add sulfuric acid methanol solution, and ultrasonically extract for $10\mathrm{min}$. The methylation step is the same as the standard working solution.

Chromatographic conditions: - Chromatographic column: HP-5 capillary column $(30.0~\mathrm{m} \times 0.25~\mathrm{mm} \times 0.25~\mu\mathrm{m})$ or equivalent polarity chromatographic column - Temperature program: initial temperature $100~^{\circ}\mathrm{C}$, maintain for $2\mathrm{min}$, increase the temperature to $240~^{\circ}\mathrm{C}$ at $15~^{\circ}\mathrm{C}/\mathrm{min}$, maintain for $5\mathrm{min}$ - Inlet temperature: $250~^{\circ}\mathrm{C}$, detector temperature: $260~^{\circ}\mathrm{C}$

Result calculation: The mass fraction $X_i$ of undecylenic acid or undecylenic acid zinc salt in the sample is calculated as follows: $$ X_{i} = \frac{m_{i}}{m \times 10^{3}} \times 100 $$