Quantification of two urinary metabolites of organophosphorus flame retardants by solid-phase extraction and gas chromatography-tandem mass spectrometry.

Trialkyl esters of phosphoric acid are widely used as flame retardants. The corresponding dialkylphosphates are formed as the main metabolites in animal experiments. We extended a previously published method for the determination of four organophosphorus flame retardant metabolites [bis(2-chloroethyl) phosphate, diphenyl phosphate, di-m-cresyl phosphate and di-p-cresyl phosphate] to be able to determine di-n-butyl phosphate (DBP) and bis(2-chloropropyl) phosphate (BCPP) in human urine samples additionally in one run. After solid-phase extraction, derivatization with pentafluorobenzyl bromide and further solid-phase cleanup, the extracts were analysed by gas chromatography-tandem mass spectrometry. The limits of detection were 0.25 microg/l for both analytes. Interday imprecisions were 2-6%. To show the applicability of the method, the internal burden of 25 persons of the population was determined. Twelve percent of the urine samples analysed tested positive for BCPP at concentrations from below the limit of detection to 0.85 microg/l; one sample contained 0.26 microg/l DBP.