Evaluation of clean-up procedures and sample dilution in multi-residue pesticide analysis of spices and herbs by UPLC-MS/MS

Abstract

ABSTRACT The matrix effect in complex spices and herbs presents a great challenge to the simultaneous, rapid, quantitative analysis of multiple pesticides by mass spectrometry. The aim of this work was to develop and validate an effective UPLC–MS/MS multi-residue method for the analysis of pesticide residues to reduce matrix effects in four spices and one herb and infer which component caused the matrix effect in black pepper. In this paper, we highlight the importance of reducing matrix effects. SPE and dilution factors combined with d-SPE were two approaches to reduce matrix effects compared with d-SPE, and dilution (5-fold) combined with d-SPE was more effective than SPE in reducing matrix effects. With the validated d-SPE method combined with dilution (5-fold), 22 pesticides showed satisfactory recovery (77 to 114%) and RSDs (1.4%–19.1%) at three spiked concentrations in dried chilli pepper, star anise, mint, and cinnamon skin, but not in black pepper. Compared to the other three spices and one herb, black pepper appeared to have a stronger matrix effect. D-SPE method combined with dilution (5-fold) was not suitable for black pepper and required more efficient purification methods and higher dilution factors. With the validated SPE method combined with 10-fold dilution, 19 pesticides showed satisfactory recovery (71% to 113%) and RSDs (2.1%–18.2%) at three spiked concentrations in black pepper. We ascertained that piperine was the component contributing most to the matrix effect in black pepper. The method was used to monitor 15 market samples.