Determination of organophosphorus flame retardants in fish by freezing-lipid precipitation, solid-phase extraction and gas chromatography-mass spectrometry

An analytical method has been developed for measuring 12 organophosphorus flame retardants (PFRs) in fish tissue samples. After the Soxhlet extraction of PFRs with dichloromethane. The experimental parameters of the clean-up were systematically optimized. Methanol was found to be a more effective solvent than acetonitrile used in freezing-lipid precipitation. Methanol (5%) in ultrapure water, was finally selected to perform solid-phase extraction (SPE, Oasis HLB cartridge), with mean lipid removal efficiency of 94% after freezing-lipid precipitation. Further purification followed by 200 mg of Z-Sep and C18 dispersant to eliminate the remaining interferences. Quantification was performed using gas chromatography-mass spectrometry in selective ion monitoring mode. The recovery, precision, and the method detection limits (MDLs) were verified by spiking experiments. All chemicals except triethyl phosphate (TEP) showed satisfactory recoveries in the range of 73-107% and 56-108% in the spiked blanks samples and spiked fish tissue samples, respectively. MDLs for PFRs in the biological samples ranged from 0.004 to 0.059 ng/g. The proposed method successfully applied to the determination of PFRs in real fish samples with recoveries of four internal standards varying from 75 to 97%. The results demonstrated that the proposed method is highly effective for analyzing PFRs in fish samples.