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

A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of ten selected pesticides in soya beans has been developed and validated The method is intended for use during the characterisation 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 C18 column 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-13C215N 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 at the Maximum Residue Limit (MRL) level (five times lower in the case of carbendazim) were in the range of 92-100% with RSDs lower than 7 %. Repeatability and intermediate precision at this level were in the range of 3.9-7.6 % and 1.9-8.7 % respectively. LODs and LOQs were 1.32-6.40 ng g-1 and 4.39-18.16 ng g-1, respectively, in the matrix. The method reliably identifies and quantifies the selected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterisation of candidate reference materials.

HUERTAS-PEREZ José;  SEJEROE-OLSEN Berit;  FERNANDEZ-ALBA A.R.;  SCHIMMEL Heinz;  DABRIO RAMOS Marta; 

2015-03-31

ELSEVIER SCIENCE BV

JRC88350

0039-9140,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC88350,   

10.1016/j.talanta.2015.01.020,