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JA0043 Effects of Temperature and Purity of Magnesium Sulfate During Extraction of Pesticide Residues Using the QuEChERS Method
来源:Journal of aoaC international | 作者:Lucia Geis-asteGGiante | 发布时间: 2065天前 | 2680 次浏览 | 分享到:
Despite its many documented advantages, the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation approach has problems with a few unstable pesticides, partly due to the exothermic reaction generated by the use of anhydrous magnesium sulfate (anh. MgSO4) during extraction. These pesticides also tend to be difficult to analyze by GC/MS. The aim of this study was to evaluate the effect of temperature during the extraction process in a revised version of AOAC Official MethodSM 2007.01 using anh. MgSO4 ≥99% (fine powder) or ≥97% (granular) purity, and the use of an ice bath for particular unstable pesticides of interest (chlorothalonil, captan, captafol, folpet, and the degradation products cis-1,2,3,6- tetrahydrophthalimide and phthalimide). Recoveries of 38 representative pesticides were measured in limes and broccoli at different extraction conditions by LC/MS/MS and low-pressure GC/MS/MS. Results showed that the difference in temperature when using ≥99% versus ≥97% purity anh. MgSO4 was 6–9°C, which did not lead to significant differences in recoveries. The use of an ice bath aided recovery for some of the analytes in broccoli, but no significant differences were observed for limes, which already provided greater stability of the basesensitive analytes due to acidity of the matrix.
1 Introduction

QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) is a very flexible sample preparation approach widely used in a variety of applications (1, 2). Modifications of this approach have been made to improve its suitability to other food samples and analytical applications like cereal grains (3), olives (4), vegetable oils (4, 5), acrylamide (6,7), clinical (8, 9), veterinary drugs (10–19), food quality (20), supplement testing (21), perfluorinated compounds (22, 23), polycyclic aromatic hydrocarbons (24–26), alkaloids (27), environmental (28–34), and mycotoxins (35, 36). In 2003, the original (37) unbuffered QuEChERS version was developed for the analysis of pesticide residues in fruits and vegetables, which is still its most common application. This original QuEChERS method has evolved to a pair of multilaboratory validated methods using acetate (AOAC Official Method 2007.01; 38) or citrate buffering (European Committee for Standardization Standard Method EN 15662; 39) to aid in the extraction and stability of certain difficult pesticides in different matrixes. In recent years, other limitations were minimized, such as the use of 7.5 mg of graphitized carbon black (GCB)/mL of extract for greater chlorophyll removal (1, 4, 37, 40, 41), better cleanup of cereal samples by a 3-fold increase in the amount of primary and secondary amine (PSA) used (3), the combination of analyte protectants to reduce analyte losses and peak tailing due to interactions with active sites in the inlet and column (42–44), the wider availability of ultra-HPLC (UHPLC) and low pressure (LP)/GC technology allowing faster analyses (3, 42, 45), and more sensitive instruments allowing the dilution of extracts to reduce matrix effects.

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