Residue Determination of β-Cypermethrin in Lettuce by Gas Chromatography

A gas chromatographic method to determine β-cypermethrin residue in lettuce was developed.The β-cypermethrin in lettuce samples were extracted with acetonitrile,then cleaned-up by Florisil solid-phase extraction columns,and eluted with n-hexane-acetone ( 9∶1,V/V).Chromatographic separation was accomplished with a heated HP-5 quartz column.The eluent was determined by GC with a micro electron capture detector(μECD)and quantified by external standard method.Under above conditions,a good linearity for β-cypermethrin existed in the range of 0.05— 2mg/L with the correlation coefficient of 0.9997.The mean recoveries ofβ-cypermethrin in lettuce ranged from 87.5% to 92.1% at the spiked levels of 1,0.5mg/kg and 0.1mg/kg,with the relative standard deviations (n= 5) of 6.7%—12.1%.The limit of detection for β-cypermethrin was 0.0008mg/kg and the limit of quantification was 0.0028 mg/kg.The method is simple,sensitive,accurate with good repeatability and practical for the residue detection and analysis of β-cypermethrin in lettuce.