Magnetic field-enhanced in-tube solid-phase microextraction on-line hyphenated with chromatography for the...

Developing on-line hyphenated technique for the sensitive and accurate monitoring of heavy metal ions (HMs) is significant and interesting. In this connection, magnetic field-enhanced in-tube solid phase microextraction technique (ME/IT-SPME) was on-line hyphenated with HPLC system for the simultaneously quantitative analysis of Ni(II), Co(II), Cu(II), Hg(II), Cr(III) and Cr(VI) in various environmental samples. To enhance the ultraviolet sensitivity, the studied HMs were reacted with sodium diethyldithiocarbamate trihydrate (DDTC) to form HMs/DDTC complexes. After that, according to the chemical properties of the complexes, 1-vinyl-3-octylimidazolium tetrafluoroborate and 2-ethylhexyl methacrylate were selected as binary functional monomers to prepare magnetic nanoparticles-doped monolithic microextraction columns for ME/IT-SPME. Results disclosed that the exertion of the magnetic field during adsorption and desorption steps enhanced the extraction efficiency of HMs from 49.0%-81.2% to 82.0%-98.9%. Under the most favorable parameters, the limits of detection for the studied HMs in water and soil samples were 0.0029-0.039 μg/L and 0.018-0.60 μg/kg, respectively. Additionally, the detailed adsorption behaviors and extraction mechanism of ME/IT-SPME towards the HMs were studied. Finally, the established on-line analytical method was successful applied to monitor the HMs contents in various environmental water and soil samples, and the method accuracy of was verified by confirmation experiments. The current work not only supplies a high-effective approach for the quantification of HMs, but also enlarges the application fields of IT-SPME technique.