Advanced oxidation using Fe3O4 magnetic nanoparticles and its application in mercury speciation analysis by high performance liquid chromatography-cold vapor generation atomic fluorescence spectrometry

Abstract

A novel, green and efficient post-column oxidation method using Fe₃O₄ magnetic nanoparticles (MNPs) was developed to on-line convert hydride generation/cold vapor generation (HG/CV) inactive species to their active species without microwave/UV irradiation. It was applied to high performance liquid chromatography HG/CV atomic fluorescence spectrometry (HPLC-HG/CV-AFS) to enable sensitive speciation analysis of both HG/CV inactive and active species. Inorganic mercury (Hg²⁺), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) were selected as model compounds to validate the methodology. Separation of these mercury species was accomplished on a RP-C18 column with a mixture of acetonitrile and water (10 : 90) at pH 6.8 containing 0.12% (m/v) L-cysteine as the mobile phase. In the presence of 0.6% (v/v) H₂O₂, on-line conversion of the organomercury species eluted from the HPLC column to Hg²⁺ was obtained using the advanced oxidation method at pH 2.0. Optimum conditions for the separation, oxidation and cold vapor generation were carefully investigated. The limits of detection (LODs) were 0.7, 1.1, 0.8 and 0.9 μg L⁻¹ (as Hg) for Hg²⁺, MeHg, EtHg and PhHg, respectively, corresponding to 14, 22, 16 and 18 pg absolute detection limits for Hg²⁺, MeHg, EtHg and PhHg by using a 20 μL sample loop, which are comparable to or better than those previously reported. National Research Council Canada DORM-2 fish muscle tissue and several real water samples were analyzed to validate the accuracy of the proposed method.