Chemometric study and optimization of headspace solid-phase microextraction parameters for the determination of multiclass pesticide residues in processed cocoa from Nigeria using gas chromatography/mass spectrometry

Solid-phase microextraction (SPME) is a solventless sample preparation method that combines sample preparation, isolation, concentration, and enrichment into one step. A simple and effective method coupling headspace-SPME to GC/MS was developed for the analysis of chlorpyrifos, fenitrothion, endosulfan I, and endosulfan II pesticide residues in cocoa powder. In this study, multivariate strategy was used to determine the significance of the factors affecting the SPME of the pesticides using a Plackett-Burman design, and the significant factors were optimized using central composite design. The analytes were extracted with 100 μm polydimethylsiloxane fibers according to the factorial design matrix and desorbed into a GC/MS instrument. The developed method was applied for the analysis of a cocoa powder sample, and it exhibited good figures of merit for the analytical methodology. Using the optimized conditions, the linearity ranged from 2.5 to 500 μg/kg (R2 > 0.99) using an internal standard calibration method, and the average recoveries were between 75 and 95%, with RSD values between 3.8 and 9.7%.