应用气相色谱法测定了小麦粉中4种有机磷和拟除虫菊类农药的残留量。样品中的残留农药用乙腈提取分离,所得提出液减压蒸发至近干,再用吹氮法蒸干。残渣用正己烷-乙酸乙酯(9+1)混合溶液2 mL溶解,所得溶液经中性氧化铝固相萃取柱净化。收集洗脱液,再用上述混合溶液10 mL淋洗固相萃取柱,收集洗脱液与上次洗脱液合并,减压蒸发至近干,再用吹氮法蒸干。用1.0 mL正己烷溶解残渣,所得溶液供气相色谱法分析用。测定中采用HP-5色谱柱,电子捕集检测器及外标法,所测4种农药的线性范围均在50~1 000 μg·L-1之间,测定下限(10S/N)均为10 μg·kg-1。在3个浓度水平上对方法的回收率作了测定,测得回收率在85.4%~95.9%之间,相对标准偏差(n=5)在2.6%~5.5%之间。

Gas chromatography was applied to the determination of residual amounts of organophosphorus and pyrethroid pesticides, i.e., phorate, chlorpyrifos, fenpropathrin and deltamethrin, in wheat flour. The pesticides were separated from wheat flour sample by extraction with acetonitrile and the extract was evaporated to near dryness under reduced pressure and then to dryness by N2-blowing. Two mL of mixed solvent of n-hexane and ethylacetate (9+1) were used to take up the residue and the solution was purified by passing through SPE column of neutral aluminum oxide. The eluate (together with the 10 mL of the same mixed solvent used as eluant to wash the column) was collected and evaporated to dryness by N2-blowing. The residue was taken up with 1.0 mL of n-hexane, which was used for GC analysis. HP-5 chromatographic column, electron capture detector and external standard method were used in the determination. Linearity ranges for the 4 presticides were found to be same between 50-1 000 μg·L-1, with same lower limit of determination (10S/N) of 10 μg·kg-1. Recovery was tested at 3 different concentration levels and values of recovery found were ranged from 85.4% to 95.9% with RSD′s (n=5) in the range from 2.6% to 5.5%.