Microfluidic desorption-free magnetic solid phase extraction of Hg2+ from biological samples using cysteine-coated gold-magnetite core-shell nanoparticles prior to its quantitation by ICP-MS

The authors describe a microfluidic method for desorption-free magnetic solid phase extraction (MSPE) of Hg2+ ions prior to their determination through ICP-MS. Nanoparticles comprising a gold core and an iron oxide (Fe3O4) shell were functionalized with L-cysteine and then used to extract trace amounts of Hg2+. In contrast to typical solid phase extraction processes, this approach is rapid and does not require a desorption step. The working pH, amount of adsorbent, sample volume, adsorption selectivity, adsorption capacity, and adsorption flow rate were optimized. Under the optimized conditions, the method was validated through determination of a certified reference material (NIST 1641d; mercury in water); the results were in good agreement. The method was applied to the analysis of (spiked) tap water and gave recoveries ranging from 101.5% to 109.3%. It was also applied to the analysis of biosamples available in limited volumes only, including cerebrospinal fluid and microdialysates.