Fabrication of benzenesulfonic acid groups modified magnetic microspheres as an MSPE adsorbent for fast determination of paraquat and diquat in human urine combined with UPLC-HRMS

In this study, novel benzenesulfonic acid groups modified magnetic microspheres (Fe3O4@SiO2@poly(4-VB)) were synthesized and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FTIR), and vibrating sample magnetometer (VSM). The as-prepared Fe3O4@SiO2@poly(4-VB) was employed as a magnetic-phase extraction (MSPE) adsorbent for rapid determination of paraquat (PQ) and diquat (DQ) in human urine samples coupled with ultra-high performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). Moreover, this paper had expounded systematically the mass spectrum cracking mechanisms of PQ and DQ. And a zwitterionic functionalized SIELC Obelisc R column was employed for separation and retention of the above two polar herbicides using 50 mmol/L ammonium formate (pH = 3.7)-acetonitrile as the mobile phase. Besides, the adsorption and desorption conditions of Fe3O4@SiO2@poly(4-VB) toward PQ and DQ were optimized in spiking urine samples to obtain the best adsorption and desorption efficiencies. And the adsorption mechanisms of Fe3O4@SiO2@poly(4-VB) toward PQ and DQ referred to synergetic effect of electrostatic attraction and π-π interaction. Under the optimal conditions, the inter-day and intra-day spiking recoveries of the proposed method were in the range of 86.7-109.9% with RSDs less than 10%. The limits of detection (LODs) were obtained by spiking in blank urine samples at a series of low concentrations and were found to be 0.12 μg/L and 0.14 μg/L for PQ and DQ, respectively, which were lower than the comparing literatures. The developed analytical method was proven to be simple, rapid, sensitive, and accurate for clinical poisoning analysis.