Development of a novel methodology for determination of dialkyl phosphates in human urine using liquid chromatography-tandem mass spectrometry

Abstract In this study a fast and sensitive method was developed for the quantitative determination of six dialkyl phosphates (DAPs) in human urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The proposed methodology was based on liquid-liquid extraction (LLE) with diethyl ether and ethyl acetate using MgSO4 and NaCl, followed by liquid chromatography and mass spectrometry detection in the selected reaction mode (SRM) with negative electrospray ionization (ESI-). Detection settings were optimized by design of experiments (DoE). Dibutyl phosphate (DBP) was used as internal standard. Several criteria established in the SANTE/11813/2017 guidance document for pesticide residues and analysis in food and feed were used to validate the suggested method: recoveries (R %) between 70-120% and coefficients of variation (CV %) ≤20%. The procedural limit of quantification (LoQ) was 0.50 ng·mL-1 for the six DAPs. The R% and CV% ranges were 82 - 117% and 3 - 20%, respectively. In total, 20 spot urine samples from lactating mothers were satisfactorily analyzed by the proposed analytical strategy.