茶叶和土壤中cis-联苯菊酯、高效氯氟氰菊酯手性对映体残留分析

Enantioseparation and Residue Analysis of cis-Bifenthrin and Lambda-Cyhalothrin in Tea and Soil

为了满足茶叶和土壤中手性农药cis-联苯菊酯和高效氯氟氰菊酯对映异构体残留检测的需要,本试验首次对比研究了正相液相色谱条件下,Daicel ChiralPak®AS-H、Phenomenex®Cellulose-1和Cellulose-3柱对两组手性对映体的拆分效果,以及气相色谱条件下BGB-172柱的分离测定效果,并建立了基于手性气相色谱分离的茶叶和土壤中cis-联苯菊酯和高效氯氟氰菊酯对映体残留分析方法。样品采用正己烷和丙酮提取,Florisil与GCB混合柱净化,气相色谱手性柱BGB-172程序升温分离,电子捕获检测器(ECD)外标法定性定量测定。结果表明,在2.5~800μg·L^(-1)浓度范围内,cis-联苯菊酯对映体色谱峰面积(Y)与浓度(x)之间分别满足线性方程Y=15381.1x-279657.5(r=0.9967)和Y=17387.6x-399048.0(r=0.9937),对映体分数(EF值)=0.489±0.017;在2.5~200μg·L^(-1)浓度范围内,高效氯氟氰菊酯对映体分别满足线性方程Y=22083.8x-161004.3(r=0.9923)和Y=23001.1x-167694.8(r=0.9922),EF=0.492±0.008。在0.005、0.050和0.50 mg·kg^(-1)3个添加浓度水平下,cis-联苯菊酯和高效氯氟氰菊酯对映体在不同茶叶、土壤样品中的平均添加回收率为61.6%~123.4%,相对标准偏差(RSD)为2.5%~14.6%,检测限低于0.001 mg·L^(-1),方法定量限低于0.005 mg·kg^(-1),不同样品中未见到明显基质效应。综上,该方法能够满足cis-联苯菊酯和高效氯氟氰菊酯对映体残留分析的需要,用于研究茶鲜叶中cis-联苯菊酯和高效氯氟氰菊酯对映体残留消解,且无明显对映体选择性差异。本研究结果为进一步开展2种手性农药在茶叶生长和加工过程中的残留和消解规律研究提供了技术支持。

In order to meet the residue analysis for cis-bifenthrin and lambda-cyhalothrin enantiomers in different tea and soil samples,the resolution and chiral separation effect for the enantiomers on Daicel ChiralPak®AS-H,phenomenex®Cellulose-1 and Cellulose-3 columns under the normal phase liquid chromatography conditions,and on a BGB-172 column under temperature programming by gas chromatography were first studied.An effective chiral analytical method was developed for the residue determination of cis-bifenthrin and lambda-cyhalothrin enantiomers in different tea and soil samples by gas chromatography electron capture detector(GC-ECD).Samples were extracted by hexane and acetone,followed by florisil and GCB mix-column purification,then separated on a BGB-172 chiral gas chromatography column with temperature programming,determined by ECD using external standard method.Within the concentration range of 2.5-800µg·L^(-1)for cis-bifenthrin enantiomers(2.5-200µg·L^(-1)for lambda-cyhalothrin enantiomers),the correlation coefficients(r)of the calibration curves were above 0.9922,and the enantiomer fractions(EFs)were 0.489±0.017 for cis-bifenthrin(0.492±0.008 for lambda-cyhalothrin),respectively.The average recoveries ranged from 61.6%to 123.4%for three fortification levels at 0.005,0.050,and 0.50 mg·kg^(-1)of cis-bifenthrin and lambda-cyhalothrin enantiomers in different tea and soil samples with the relative standard deviations(RSDs)between 2.5%and 14.6%.The limits of detection(LODs)were lower than 0.001 mg·L^(-1),and the limits of quantification(LOQs)were lower than 0.005 mg·kg^(-1).It was investigated that there was no matrix effect by comparing the responds of matrix-standard and solvent-standard solution.This method can be used to evaluate environmental residues and the safety of agricultural products.There was no significant enantioselectivity degradation differences for each enantiomer residue of cis-bifenthrin and lambda-cyhalothrin in fresh tea leaves at field trials.This method provides technical support on the residues and digestion patterns of two chiral pesticides during the growth and processing of tea.