Chromatography and Separation Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
J Agric Food Chem. 2010 May 26;58(10):5950-8. doi: 10.1021/jf902988b.
A simple method was evaluated for the determination of pesticide residues in flaxseeds, doughs, and peanuts using gas chromatography-time-of-flight mass spectrometry (GC-TOF) for analysis. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, which was previously optimized for cereal grain samples, was evaluated in these fatty matrices. This extraction method involves first mixing the sample with 1:1 water/acetonitrile for an hour to swell the matrix and permit the salt-out liquid-liquid partitioning step using anhydrous MgSO(4) and NaCl. After shaking and centrifugation, cleanup is done by dispersive solid-phase extraction (d-SPE) using 150 mg of anhydrous MgSO(4), 150 mg of PSA, and 50 mg of C-18 per milliliter of extract. This method gave efficient separation of pesticides from fat and removal of coextracted substances better than gel permeation chromatography or use of a freeze-out step, which involved excessive use of solvent and/or time. The optimized analytical conditions were evaluated in terms of recoveries, reproducibilities, limits of detection, and matrix effects for 34 representative pesticides using different types of flaxseeds, peanuts, and doughs. Use of matrix-matched standards provided acceptable results for most pesticides with overall average recoveries between 70 and 120% and consistent RSDs <20% for semipolar pesticides and <26% for lipophilic pesticides. The recoveries of these latter types of pesticides depended on the fat content in the matrices and partitioning factor between the lipids and acetonitrile. We believe that the consistency of the pesticide recoveries for different samples in multiple experiments and the physicochemical partitioning explanation for <70% recoveries of lipophilic pesticides justify compensation of results for the empirically determined recovery values. In any case, this method still meets 10 ng/g detection limit needs for lipophilic pesticides and may be used for qualitative screening applications, in which any identified pesticides can be quantified and confirmed by a more intensive method that achieves >70% recoveries for lipophilic pesticides.
一种简单的方法被评估用于使用气相色谱飞行时间质谱(GC-TOF)分析亚麻籽、面团和花生中的农药残留。先前针对谷物样品进行了优化的改良 QuEChERS(快速、简单、廉价、有效、耐用和安全)方法在这些脂肪基质中进行了评估。该提取方法首先将样品与 1:1 的水/乙腈混合一小时,使基质膨胀,并使用无水硫酸镁和氯化钠进行盐析液液分配步骤。摇匀和离心后,通过分散固相萃取(d-SPE)进行净化,每毫升提取物使用 150 mg 无水硫酸镁、150 mg PSA 和 50 mg C-18。与凝胶渗透色谱或使用冷冻步骤相比,这种方法能够更好地从脂肪中有效分离农药并去除共提取物质,凝胶渗透色谱或冷冻步骤需要大量使用溶剂和/或时间。使用不同类型的亚麻籽、花生和面团,针对 34 种代表性农药,根据回收率、重现性、检测限和基质效应,优化了分析条件。使用基质匹配标准为大多数农药提供了可接受的结果,总体平均回收率在 70%至 120%之间,对于半极性农药,RSD 一致<20%,对于亲脂性农药,RSD<26%。这些亲脂性农药的回收率取决于基质中的脂肪含量和脂类与乙腈之间的分配因子。我们认为,不同样品在多次实验中的农药回收率的一致性以及对<70%亲脂性农药回收率的理化分配解释证明了经验确定的回收率值的补偿是合理的。在任何情况下,该方法仍然满足亲脂性农药 10 ng/g 的检测限要求,并且可用于定性筛选应用,其中任何识别出的农药都可以通过回收率>70%的更密集方法进行定量和确认亲脂性农药。