Development and application of UPLC-Q-Orbitrap HRMS methods for the determination of eight metabolites of p-chloronitrobenzene in human urine

Accurate, reliable, and sensitive methods for the determination of eight metabolites of p-chloronitrobenzene (p-CNB) were developed based on ultra-performance liquid chromatography − quadrupole − orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). The free and conjugated forms of metabolites were determined before and after urine samples were hydrolyzed with acid. Subsequently, three solid phase extraction steps were used for concentration and purification. The calibration curves of the eight metabolites exhibited good linearity with an R² of >0.999, and the precision was good as well, with the coefficient of variations of intra-day and inter-day being lower than 7.0 % and 8.5 %, respectively. Analytical accuracy for all metabolites varied within ranges of 76.0–102.9 %, and the limit of detection and limit of quantification of all the metabolites varied within ranges of 0.2–7.7 μg/L and 0.6–25.6 μg/L in human urine, respectively. In addition, the application potential of the proposed methods were evaluated by applying them to the determination of metabolites in the urine of workers exposed to p-CNB, and these results showed that these methods were accurate, reliable, and sensitive, which makes them an excellent choice for detecting the metabolites of p-CNB in the urine of exposed workers.