Compensation of matrix effects in seed matrices followed by gas chromatography-tandem mass spectrometry analysis of pesticide residues

Abstract

Despite analytical advances, matrix effects (MEs) in pesticide residue analysis by gas chromatography – tandem mass spectrometry continue to be a challenge, especially in difficult samples such as seeds. In this study, the influence of different clean-up sorbents (chitin, chitosan, Z-Sep+, EMR-Lipid) and different mixtures of primary secondary amine (PSA), C18, graphitized carbon black (GCB) and MgSO4 were investigated in terms of MEs and recoveries in four types of seeds: cress, fennel, flax, and hemp. Additionally, different volumes of water (5, 7.5 and 10 mL) were investigated for QuEChERS extraction. Under the selected conditions: the largest volume of water (10 mL) and PSA/C18/GCB/MgSO4 (50/150/50/50 mg, respectively) as clean-up sorbent yielded acceptable recoveries of 70–120% for most of the pesticides (211–225 out of 248 compounds) and the lowest MEs were between −20%>MEs>20% (27–50 compounds). The final method was validated for 248 pesticides with LOQs equal to 0.005 mg kg−1. Additionally, matrix-matched calibration was used as a practical method to compensate for MEs. Among the 21 pesticides found in 12 of the samples, chlorpyrifos (0.008–1.1 mg kg−1), tebuconazole (0.071–0.96 mg kg−1), and trifloxystrobin (0.007–0.15 mg kg−1) were most commonly determined.