Determination of twenty pesticides in rice by employing QuEChERS and LC-ESI-MS/MS

This paper describes a method for the determination of twenty pesticides in rice grains by liquid chromatography-tandem mass spectrometry with electrospray ionization in positive mode (LC-MS/MS). The QuEChERS method was used for the extraction of pesticides and clean-up of samples. Using a phenyl-based chromatographic column and a gradient of mobile phase composed of acetonitrile-water (95/5, v/v) and formic acid 0.1%, the analytical method was optimized with a total run time of 15 min. MS/MS parameters were optimized to provide higher sensitivity for each compound, resulting in limits of detection and quantification in the ranges of 0.1-17.6 ng mL(-1) and 0.4-58.8 ng mL(-1), respectively. The performance of the method was also evaluated in terms of linearity, precision (instrumental, intra-assay and inter-assay), and accuracy (recovery), and then it was applied to eight commercial rice samples from different suppliers. The results demonstrated the ability of the method to detect all the 20 pesticides with precision and accuracy according to the protocols established by the most important organizations and validation guidelines. Furthermore, the limits of quantification of the method were expressively lower than the maximum residue limit (MRL) established by the Brazilian Health Surveillance Agency (ANVISA) for these pesticides in rice grains, which allow its application for monitoring real samples.