Matrix effect evaluation and method validation of organophosphorus pesticide residues in bell peppers (Capsicum annuum L.) by GC-MS determination

The matrix effects in bell pepper samples were studied. The simultaneous determination of six organophosphorus (OPPs) pesticides (chlorpyrifos, dichlorvos, disulfoton, ethoprophos, fenchlorphos, and prothiofos), by gas chromatography-mass spectrometry (GC/MS) method using sample preparation on QuEChERS-citrate, was developed and validated. Non-organic and organic bell peppers (Capsicum annuum L.) samples were analysed. Matrix-matched calibrations were established to correct matrix effect (ME) for quantification analysis of the six pesticides. All of the pesticides showed matrix-induced signal suppression, where chlorpyrifos and prothiofos were the pesticides that presented the most significant values, -65.54 and -65.31, respectively. The pesticides studied showed good linearity with correlation coefficient values higher than 0.99. The LODs ranged from 0.002 to 0.039 mg kg-1 and LOQs 0.006 to 0.130 mg kg-1. Only one sample of the bell pepper showed contamination with chlorpyrifos (0.177 mg.kg-1), corresponding to a value 17.7 times higher than the MRLs allowed for this crop by European Committee (EC) (0.010 mg.kg-1).