Chemometric study and optimization of extraction parameters in single-dropmicroextraction for the determination of multiclass pesticide residues in grapesand apples by gas chromatography mass spectrometry

摘要

A simple and rapid single-drop microextraction method coupled with gas chromatography and massspectrometry (SDME-GC/MS) for the determination of 20 pesticides with different physicochemicalproperties in grapes and apples was optimized by the use of a multivariate strategy. Emphasis on the opti-mization study was given to the role of ionic strength, sugar concentration and pH of the donor samplesolution prepared from the fruit samples. Since all three variables were found to affect negatively SDME(a lower extraction efficiency was observed as the values of variables were increased for most of thepesticides studied), donor sample solution was optimized using a central composite design to evaluatethe optimum pH value and the optimum dilution of the sample extract. With some exceptions (chlorpyri-fos ethyl, a-endosulfan,β-endosulfan, pyriproxyfen, λ-cyhalothrin and bifenthrin), the optimum methodincluded the dilution of the analytical sample by 12.5-fold with a buffered acetone/water solution at pH = 4and exhibited good analytical characteristics for the majority of target analytes (pyrimethanil, pirimi-carb, metribuzin, vinclozolin, fosthiazate, procymidone, fiudioxonil, kresoxim methyl, endosulfan sulfate,fenhexamid, iprodione, phosalone, indoxacarb and azoxystrobin) by providing high enrichment factors(14-328), low limits of detection (0.0003-0.007 p.g/g), and good precision (relative standard deviationsbelow 15%).