Optimization and validation of a single method for the determination of pesticide residues in Peumus boldus Molina leaves using GC-MSD, GC-MS/MS and LC-MS/MS

Abstract The QuEChERS methods, CEN 15662 and AOAC 2007.01, and different clean-up variations were applied to the determination of pesticide residues in Peumus boldus Molina leaves, using LC and GC coupled to single and tandem mass spectrometry. Boldo belongs to the class of medicinal and aromatic plants. Because of its complex chemical composition including terpene peroxides, alkaloids and phenolic acids at concentrations typically 100-fold higher than that of a possible contaminant, it is a very challenging matrix for pesticide residue determination. Thin layer chromatography was used to evaluate the efficacy of removal of matrix co-extractives using different clean-up sorbents, including neutral alumina, graphitized carbon black (GCB), octadecyl reverse phase silica gel (RP-C18) and pH modification in the extraction and clean-up steps. The most promising method was a combination of GCB, RP-C18 and primary-secondary amine (PSA) within the QuEChERS template. The final optimized method was validated according to the SANTE guidelines using LC-MS/MS and GC-MS/MS. The method scope includes 84 representative pesticide residues with recoveries ranging from 70 to 119% and within laboratory relative standard deviations below 15%. The method was initially validated for 25 representative pesticides using GC-MSD, making it applicable in those laboratories equipped only with a single mass detector. It is important to emphasize that the method complies with the requirements of international pharmacopoeias and food regulatory agencies, since herbal teas are found in both categories, as herbal remedies and foods.