Simultaneous determination of 11 organophosphorus flame retardants and 6 metabolites in human urine by ultra-performance liquid chromatography tandem mass spectrometry

Organophosphorus flame retardants (OPFRs) are widely used chemicals with significant health risks to humans. OPFRs are metabolized and excreted primarily through urine, making urine a key matrix for assessing human exposure levels. Therefore, this study developed a method combining the Quick, Easy, Cheap, Effective, Rugged, Safe (QuEChERS) approach with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for the simultaneous determination of 11 OPFRs and 6 organophosphorus flame retardant metabolites (mOPFRs) in human urine. All target compounds exhibited excellent linearity, with correlation coefficients (r²) exceeding 0.9988. The limits of detection (LODs) and the limits of quantification (LOQs) ranged from 0.01 ng/mL to 0.05 ng/mL and 0.03 ng/mL to 0.16 ng/mL, respectively. Except for tricresyl phosphate (<50 %), the spiked recoveries for the other target compounds were 51.4–117 %, 52.4–100 %, 63.9–128 %, and 89.0–112 % at four concentration levels. All analytes showed intra-day and inter-day precision with relative standard deviations (RSDs) of 0.8–18.8 % and 1.4–12.2 %, respectively. Analysis of children’s urine revealed distinct metabolic patterns: triphenyl phosphate and tris(1,3-dichloro-2-propyl) phosphate were not detected, while their metabolites, diphenyl phosphate and bis(1,3-dichloro-2-propyl) phosphate, were found in the urine. In contrast, tris(2-butoxyethyl) phosphate, tributyl phosphate, tri(2-chloroethyl) phosphate, and tris(1-chloro-2-propyl) phosphate suggested possible co-occurrence of parent compounds and metabolites. The developed method is simple, sensitive and robust, and has the advantage of high throughput for screening 17 targets including parent compounds and metabolites. These features make it suitable for assessing the exposure risk of OPFRs in urine.