Development of MOF-808 based dispersive solid-phase extraction and ultra-high performance liquid chromatography tandem mass spectrometry for monitoring organophosphate diesters in urine

Urinary organophosphate diesters (di-OPEs) serve as characteristic biomarkers for human exposure to organophosphate triesters (tri-OPEs). Existing sample pretreatment technologies for simultaneously extracting various di-OPEs in urine may be affected by the limited specific interactions and complicated urinary matrix interference, resulting in suboptimal recoveries. To establish a high-throughput and multi-target tool for monitoring urinary di-OPEs, zirconium-based metal organic framework MOF-808 was hydrothermally fabricated as dispersive solid-phase extraction (DSPE) adsorbents, and coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for quantification. MOF-808 exhibited maximum adsorption capacities of 108∼133 mg g^−‍1 for target di-OPEs with a rapid adsorption equilibrium time of 30 min. The calculated adsorption energies between MOF-808 and di-OPEs ranged from −56.7 to −87.1 kJ mol⁻¹, which were primarily driven by the synergistic effects of hydrogen bonding and π-π stacking. Under determined DSPE parameters, the developed DSPE-UPLC-MS/MS technology showed ideal linearity ranged from 0.05 to 50.0 ng mL^−‍1, with limits of detection (LODs) of 0.02–0.45 ng mL^−‍1, spiked recoveries of 75.6 %∼121.8 %, and matrix effects of 67.9 %∼121.0 %. This technology was successfully validated through the detection of twelve di-OPEs in 24-h pooled urine samples from college students, demonstrating the detection frequencies of 13.9 %–100 %, and specific gravity (SG)-adjusted median concentrations ranging from 0.09 to 7.62 ng mL⁻¹. Notably, six urinary di-OPEs exhibited significantly higher levels in females than males (P < 0.05). Overall, this newly proposed DSPE-UPLC-MS/MS technology enabled simultaneous quantification of twelve di-OPEs in urine.