Magnetism-reinforced in-tube solid phase microextraction for the online determination of trace heavy metal ions in...

For the first time, a convenient, online couplable, sensitive and environmentally friendly sample pretreatment method, namely, magnetism-reinforced in-tube solid phase microextraction (MR/IT-SPME) was proposed to effectively enrich heavy metal ions (HMIs). Monolithic capillary microextraction column embedded modified Fe₃O₄ magnetic nanoparticles (MCEN) was conveniently synthesized and employed as the microextraction column of MR/IT-SPME. Subsequently, the MCEN was put into a magnetic coil which was utilized to exert variable magnetic field during extraction procedure. Three HMIs, including Cu(II), Co(II) and Hg(II), were selected as studied ions and reacted with chelating agent sodium diethyldithiocarbamatetrihydrate to form metallic coordination compounds. The complexes were infused to the MCEN to perform the MR/IT-SPME extraction and then online determined by high-performance liquid chromatography equipped with diode array detection (HPLC-DAD). A series of key parameters affecting the extraction performance were investigated in detail. Results revealed that the exertion of magnetic field in adsorption and desorption steps favored the adsorption and release of the coordination compounds, with the extraction efficiencies enhanced from 47-65% to 67-89%. Finally, the developed online MR/IT-SPME-HPLC-DAD approach was successfully applied to determine studied HMIs in environmental water and seafood samples. The confirmatory experiments further evidenced the reliability and feasibility of the introduced approach for the analysis of trace HMIs in complex samples.