Determination of methylmercury and inorganic mercury by coupling short-column ion chromatographic separation, on-line photocatalyst-assisted vapor generation, and inductively coupled plasma mass spectrometry

We have combined short-column ion chromatographic separation and on-line photocatalyst-assisted vapor generation (VG) techniques with inductively coupled plasma mass spectrometry to develop a simple and sensitive hyphenated method for the determination of aqueous Hg2+ and MeHg+ species. The separation of Hg2+ and MeHg+ was accomplished on a cation-exchange guard column using a glutathione (GSH)-containing eluent. To achieve optimal chromatographic separation and signal intensities, we investigated the influence of several of the operating parameters of the chromatographic and photocatalyst-assisted VG systems. Under the optimized conditions of VG process, the shortcomings of conventional SnCl2-based VG techniques for the vaporization of MeHg+ was overcome; comparing to the concentric nebulizer-ICP-MS system, the analytical sensitivity of ICP-MS toward the detection of Hg2+ and MeHg+ were also improved to 25- and 7-fold, respectively. With the use of our established HPLC–UV/nano-TiO2–ICP-MS system, the precision for each analyte, based on three replicate injections of 2 ng/mL samples of each species, was better than 15% RSD. This hyphenated method also provided excellent detection limits—0.1 and 0.03 ng/mL for Hg2+ and MeHg+, respectively. A series of validation experiments—analysis of the NIST 2672a Standard Urine Reference Material and other urine samples—confirmed further that our proposed method could be applied satisfactorily to the determination of inorganic Hg2+ and MeHg+ species in real samples.