低温提取气相色谱法测定大葱中辛硫磷

Extraction of Phoxim in Welsh Onion Under Low Temperature and Its Determination by Gas Chromatography

建立了气相色谱法测定大葱中辛硫磷残留量的分析方法。大葱样品经冷冻后,采用约2℃乙腈提取,提取液盐析后浓缩供气相色谱分析。由于辛硫磷的热不稳定性,通过优化气相色谱条件,可减少热分解,提高响应值,辛硫磷的质量浓度在0.10-10.0 mg·L^-1范围与峰面积呈线性关系（r=0.999 9）,方法的检出限为0.01 mg·kg^-1,在0.02-0.10 mg·kg^-1添加水平回收率为83.1%-105.0%,相对标准偏差为2.6%-9.2%。

Residual phoxim in welsh onion was extracted with acetonitrile at about 2℃, and the extract was evaporated to nearly dryness after salting out with sodium chloride. The residue was taken up with 1 mL of acetone and was ready for GC determination. Considering the thermoinstability of pboxim, the conditions of gaschromatography were optimized to reduce its thermo-decomposition and to raise response value. Linear relationship between the peak area and concentration of pboxim was kept in the range of 0. 10-10. 0 mg·L^-1（r= 0. 999 9）, with its detection limit of 0. 01 mg·kg^-1. Recovery tests were made by addition of standard pboxim in the concentration range of 0. 02 to 0. 10 mg·kg^-1 , and the values of recovery obtained were in the range 88. 1% - 105. 0%, and precision tests were also performed, giving values of RSD＇s （n=6） in the range of 2. 6%-9.2%.