Chip-Based Magnetic Solid-Phase Microextraction Online Coupled with MicroHPLC-ICPMS for the Determination of Mercury Species in Cells

Trace mercury speciation in cells is critical to understand its cytotoxicity and cell protection mechanism. In this work, we fabricated a chip-based magnetic solid-phase microextraction (MSPME) system, integrating a cell lysis unit as well as a sample extraction unit, and online combined it with micro high-performance liquid chromatography (microHPLC) inductively coupled plasma mass spectrometry (ICPMS) for the speciation of mercury in HepG2 cells. Magnetic nanopartides with sulfhydryl functional group were synthesized and selfassembled in the microchannels for the preconcentration of mercury species in cells under an external magnetic field. The enrichment factors are ca. 10-fold, and the recoveries for the spiked samples are in the range of 98.3-106.5%. The developed method was used to analyze target mercury species in Hg+ or MeHg+ incubated HepG2 cells. The results demonstrated that MeHg+ entered into the HepG2 cells more easily than Hg, and part of the MeHg+ might demethylate into Hg2+ in HepG2 cells. Besides, comprehensive speciation of mercury in incubated cells revealed different detoxification mechanisms of Hg2+ and MeHg+ in Hg2+ or MeHg+ incubated HepG2 cells.