Method Development, Optimization and Validation of Matrix Hydration Effect on Pesticide Residues in Cocoa Beans Using Modified QuEChERS Method and Gas Chromatography Tandem Mass Spectrometry

Modified QuEChERS method combined with gas chromatography tandem mass spectrometry (GC-MS/MS) was developed and validated to determine pesticide residues in dried cocoa beans. Extraction efficiency of matrix hydration effect on 19 pesticide residues was studied and optimized using 2(3) full factorial design with percentage recoveries as the response variable. The optimized hydration method was validated for 24 pesticides, and recoveries obtained were in the range of 70-120% with relative standard deviations of less than 20% for most pesticides. Limit of quantification was obtained at 10 mu g/kg for all pesticides, and this value was lower than national maximum residue levels (MRLs). Finally, the developed and optimized method was applied to real cocoa bean samples and the results from incurred residues were compared between method with and without matrix hydration. These results suggest that the addition of water to the dry and high-fat cocoa bean samples is crucial in pesticide residue analysis.