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 μL−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 μL−1, with coefficient of determination (R2) from 0.977 to 0.994, depending on target analytes. Calculated decision limit (CCα) and detection capability (CCβ) for fipronil, sulfone and sulphide were in the range 0.05–0.16 and 0.28–0.73 pg μL−1 respectively.