Development, validation and evaluation of matrix effect of a QuEChERS-based multiresidue method with low temperature dispersive clean-up for analysis of 104 pesticides in cumin (Cuminum cyminum) by LC-MS/MS

BACKGROUND Until now, there is no method available for analysis of pesticide residues in complex matrices like spices. Therefore, there is an urgent need to develop and validate a QuEChERS-based method for the estimation of 104 pesticides in cumin seed. RESULTS Samples were spiked for 109 pesticides at concentrations of 0.1, 0.5 and 1.0 mg kg(-1). Of these 104 pesticides were recovered. At 0.1, 0.5 and 0.1 mg kg(-1), recoveries ranged from 71% to 108% when compared with matrix matched standards. Seventeen pesticides showed higher or lower recoveries than acceptable range (70-120%) when quantified using solvent standards showing significant matrix effect (ME) (>= +/- 20%) even after 20x dilution. However, for the other pesticides ME was significantly eliminated on dilution. The recovery percentage improved for all pesticides on quantitation with matrix matched standards when compared with solvent standards. For pesticides with lower European Union (EU) maximum residue limits (MRLs), an experiment at lower spiking concentrations of 0.01 and 0.05 mg kg(-1) with lower dilutions (8x) reveals that almost all pesticides with lower EU MRLs (0.02 and 0.05 mg kg(-1)) showed recoveries in the range 74-124% and relative standard deviation (RSD) less than 20%. CONCLUSION Theoretical limit of quantitation (LOQ) is proposed which ranged from 0.01 to 0.18 mg kg(-1) for matrix matched standards. An LOQ of 0.01 mg kg(-1) was easily achieved for the pesticides with lower EU MRLs with lower dilutions (8x) with exception of fipronil for which this can be achieved without dilution provided matrix matched standards are used. The method can be extended to other spices. (c) 2021 Society of Chemical Industry.