Development and validation of a method for fipronil residue determination in ovine plasma using 96-well plate solid-phase extraction and gas chromatography-tandem mass spectrometry

Fipronil, a phenylpyrazole insecticide introduced for pest control on a broad range of crops, undergoes a reinforcement of the regulation within the European Union (2007/52/EC directive) due to its potential effects on environment and human health. In order to assess the plasmatic concentrations of fipronil residues (sulfone, sulfide, fipronil, desulfinyl and amide) in ovine, a methodology based on gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) was developed and validated according to the European standard (2002/657/EC). The proposed method allows a large number of samples to be treated concurrently (n=80) using a reduced sample amounts (0.2 mL), and consents to reach a level of quantification of 0.1 pg mu L-1. The sample preparation consisted of a single solid-phase extraction (SPE) purification on a 96-well plate filled with a styrene-divinyl-benzene phase. Linearity was demonstrated all along the investigated range of concentrations, i.e. from 0.25 to 2000 pg mu L-1, with coefficient of determination (R-2) from 0.977 to 0.994, depending on target analytes. Calculated decision limit (CC alpha) and detection capability (CC beta) for fipronil, sulfone and sulphide were in the range 0.05-0.16 and 0.28-0.73 pg mu L-1 respectively. (c) 2008 Elsevier B.V. All rights reserved.