Determination of fipronil and its three degradates in water using stir bar sorptive extraction-thermal desorption-gas chromatography-tandem mass spectrometry.

A method was developed for determination of fipronil (FIP) pesticide and its three major degradates (fipronil desulfinyl, fipronil sulfide, fipronil sulfone) in water at the levels required by the EU Commission in the Decision 2022/1307. The method combines solvent-free stir bar sorptive extraction (SBSE) with thermal desorption-gas chromatography-tandem mass spectrometry (TD-GC-MS/MS). Simple sample processing involves 16 h of stirring a 100 mL water sample with a polydimethylsiloxane-coated sorptive stir bar, followed by TD of the trapped analytes into the GC. The greenness assessment by analytical Eco-Scale approach resulted in classification of the entire analytical method as "an excellent green analysis". The obtained limits of quantification for all FIPs determined in tap, lake, MilliQ water and artificial seawater were in the range of 0.12-0.30 ng L. The recoveries ranged between 81.7 and 109% with relative standard deviations from 2.8 to 14%. The results show that the method is suitable for screening and monitoring the studied analytes in selected matrices.