Application of the QuEChERS procedure and LC-MS/MS for the assessment of neonicotinoid insecticide residues in cocoa beans and shells

The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure was applied and validated for the analysis of neonicotinoid insecticide residues in cocoa bean matrix with high fat and high pigments. Samples employed in the study were fermented and dried beans obtained from major cocoa producing regions in Ghana where neonicotinoids are extensively used. Shells covering the beans were removed and analyzed separately to examine insecticide distribution. Analytes in both matrices were extracted in acetonitrile with sodium acetate and magnesium sulfate salts, cleaned up using a sorbent mixture of primary secondary amine (PSA), C18 and graphitized carbon black (GCB), and quantified using liquid chromatography tandem mass spectrometry (LC-MS/MS). Average recoveries at four levels of fortification ranged from 92 to 111% with relative standard deviation of ≤16% for all analytes. Limits of quantification ranged from 3 to 10 μg/kg for all neonicotinoids. Imidacloprid was the most frequently encountered neonicotinoid and was quantified in more than 10% of deshelled bean and 30% of cocoa shell samples, with concentrations ranging from 11.5 to 35.6 μg/kg and 11.8 to 214 μg/kg in cocoa beans and shells, respectively. The findings from this study suggest a need for greater efficiency in neonicotinoid application, to avoid the build-up of these insecticides to unsafe levels in cocoa beans.