固相萃取-气相色谱法测定茶叶中甲胺磷残留量

茶叶样品经乙酸乙酯提取,上清液于50℃蒸发至近干,加入乙酸乙酯溶解残渣后,经硅胶-石墨化碳混合柱净化。先以乙酸乙酯洗脱去除杂质,再以碱化乙腈洗脱并收集流出液,在50℃蒸发至近干,加乙酸乙酯定容至1mL,供气相色谱分析。采用DB-1701色谱柱分离和火焰光度检测器检测,所得甲胺磷的线性范围为0.010～1.00mg·L-1,方法的检出限(3S/N)为0.005mg·kg-1。在0.010,0.020,0.080 mg·kg-1 3个浓度水平下进行回收试验,甲胺磷的回收率在85.0%～90.9%之间,相对标准偏差(n=6)在2.2%～4.3%之间。

GC Determination of Residual Amount of Methamidophos in Tea with Solid Phase Extraction

Sample of tea was extracted with ethyl acetate,and the supernatant was taken and evaporated to near dryness at 50 ℃.The residue was dissolved with ethyl acetate,and purified by passing through a column packed with silica gel and graphitized carbon.The column was washed with ethyl acetate to remove impurities,and then eluted the analyte with alkalified acetonitrile.The eluate obtained was evaporated to near dryness at 50 ℃,and taken up with 1 mL of ethyl acetate and used for GC analysis using the DB-1701 chromatographic column for separation and FPD for detection.Linearity range of methamidophos was kept between 0.010-1.00 mg·L-1,with detection limit(3S/N) of 0.005 mg·kg-1.Tests for recovery and precision were made by addition of 0.010,0.020,0.080 mg·kg-1 of standard solution,and analyzed by the proposed method,giving values of recovery in the range of 85.0%-90.9% and values of RSD′s(n=6) in the range of 2.2%-4.3% respectively.