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 rnethod 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. (C) 2009 Elsevier B.V. All rights reserved.