A novel, green and efficient post-column oxidation method using Fe(3)O(4) 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 (Hg(2+)), 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) H(2)O(2), on-line conversion of the organomercury species eluted from the HPLC column to Hg(2+) 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 Hg(2+), MeHg, EtHg and PhHg, respectively, corresponding to 14, 22, 16 and 18 pg absolute detection limits for Hg(2+), 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.

A new, miniaturized and low power consumption photochemical vapor generation (PVG) technique utilizing an ultraviolet light-emitting diode (UV-LED) lamp is described, and further validated via the determination of trace mercury. In the presence of formic acid, the mercury cold vapor is favourably generated from Hg(2+) solutions by UV-LED irradiation, and then rapidly transported to an atomic fluorescence spectrometer for detection. Optimum conditions for PVG and interferences from concomitant elements were investigated in detail. Under optimum conditions, a limit of detection (LOD) of 0.01 μg L(-1) was obtained, and the precision was better than 3.2% (n = 11, RSD) at 1 μg L(-1) Hg(2+). No obvious interferences from any common ions were evident. The methodology was successfully applied to the determination of mercury in National Research Council Canada DORM-3 fish muscle tissue and several water samples.

An ultrasensitive, simple and interference-free method using nano-TiO 2 preconcentration and in situ slurry hydride generation (HG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of trace selenium. Total Se reduced in Se(IV) form can be selectively adsorbed on TiO 2 at pH < 8 for pre-concentration, and then separated and slurried/released by a mixture containing 3% (m/v) KBH 4 and 1% (m/v) KOH. The slurry solution was mixed with 25% (v/v) HCl to generate selenium hydrides, which was subsequently separated from the liquid phase for subsequent AFS detection. Optimum conditions for adsorption, disadsorption and hydride generation of selenium as well as potential interferences from concomitant ions were investigated. Due to the repulsive force between the positively charged TiO 2 and metal cationic ions, this approach permits 1000 mg L À1 for Fe 3+ , Ni 2+ and Co 2+ , 500 mg L À1 for Cu 2+ or 100 mg L À1 for Ag + and Au 3+ present in a 5 mg L À1 Se(IV) solution without any significant interferences. A limit of detection of 0.0006 mg L À1 was obtained by sampling a 40 mL sample solution. Compared to the conventional HG method, the sensitivity and the limit of detection were improved 17-and 16-fold by the present method, respectively. The proposed method was successfully applied for the determination of trace selenium in several real samples.

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A new digestion method using UV-assisted Fe(0) Fenton reaction was developed for the determination of trace Cd in rice by hydride generation atomic fluorescence spectrometry. The proposed method integrated the advantages of simplicity, small dose of reagents, low cost and moderate reaction conditions, and was successfully utilized to analyze a Certified Reference Material (CRM) and real rice samples. A 1 mL mixture of the sample and reagents (0.0500 g rice powder, 0.2% (m/v) Fe(0), 0.75% (v/v) HNO3 and 18% (v/v) H2O2) was irradiated by UV-light for 50 min and then a clear solution was obtained by separating excess Fe(0) with a magnet prior to spectral analysis. The limit of detection (LOD) for Cd was found to be 0.02 mg kg(-1) and the relative standard deviation was better than 5.0% at a concentration level of 0.40 mg kg(-1). The recovery obtained by analyzing the CRM was 103% and spiked recoveries with 0.40 mg kg(-1) Cd in rice samples were 93% and 101%. The t-test proved that there is no significant difference between the certified value and the determined value of the CRM, and between the proposed method and microwave-assisted digestion coupled with inductively coupled plasma mass spectrometry (MWD-ICP-MS) at 95% confidence level.