Analysis of perfluorinated compounds in biota by microextraction with tetrahydrofuran and liquid chromatography/ion isolation-based ion-trap mass spectrometry

An analytical method combining both a simple, fast and efficient solvent microextraction and a sensitive and selective monitoring mode, based on ion isolation ion-trap mass spectrometry (MS), was developed for analysis of perfluorinated compounds (PFCs) in biota. The method involved the vortex-shaking of 0.2 g of tissue sample and 800 μL of tetrahydrofuran (THF):water (75:25, v/v) for 7 min, subsequent centrifugation for 13 min and direct quantitation of PFCs in the extract against solvent-based calibration curves. Selection of solvent composition was based on Hildebrand solubility parameters and their components (i.e. dispersion, dipole–dipole and hydrogen bonding forces). Recoveries in samples for PFCs with hydrocarbon chain lengths between C₄ and C₁₄ ranged from 85 to 111%, with relative standard deviations between 1 and 11%. The ion isolation monitoring mode, proposed for the first time for ion-trap-MS quantitation, proved to be effective in avoiding space-charge effects caused by co-eluting matrix components while keeping the sensitivity of full scan MS operation. Detection limits of the method were in the range 0.8−6 ng g⁻¹ for perfluoroalkyl carboxylates (PFACs) and 0.4–0.8 ng g⁻¹ for perfluoroalkyl sulfonates (PFASs) in wet weight samples. The method was validated using a reference material made up of flounder muscle and by comparison with triple quadrupole MS measurements and it was applied to the determination of PFCs in liver and muscle samples from sea birds and fishes. Only PFASs were found in samples at quantifiable levels (2.9 and 13.1 ng g⁻¹) while PFACs were below the respective quantitation limits. This method allows quick and simple microextraction of PFCs with minimal solvent consumption, while delivering accurate and precise data.