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Accurate determination of selected pesticides in soya beans by liquid chromatography coupled to isotope dilution mass spectrometry

J.F. Huertas Pérez, B. Sejerøe-Olsen, A.R. Fernández Alba, H. Schimmel, M. Dabrio. 

Talanta Volume 137, 15 May 2015, Article number 15348, Pages 120-129

DOI: 10.1016/j.talanta.2015.01.020

Abstract 

A sensitive, accurate and simple liquid chromatography coupled with mass spectrometrymethod for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18column using gradient elution with water-methanol/2.5 mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-13C2 15N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005 mg kg-1 in the matrix, while LOQs established as the lowest spiking massfractionation level were in the range 0.01-0.05 mg kg-1. The method reliably identifies and quantifies theselected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterization of candidate reference materials.

© 2015 The Authors.

 

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Published 25-04-2016, 20:17:32

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