Mercury speciation by HPLC-cold-vapour radiofrequency glow-discharge optical-emission spectrometry with on-line microwave oxidation

Hollow-cathode (HC) radiofrequency glow-discharge (rf-GD) optical-emission spectrometry (OES) has been used as detector for the determination of inorg anic mercury by cold-vapour (CV) generation in a flow-injection (FI) system . Both NaBH4 and SnCl2 were evaluated as reducing reagents for production o f mercury CV. The conditions governing the discharge (pressure, He flow rat e, and delivered power) and Hg CV generation (NaBH4 or SnCl2 concentration and reagent flow rate) were optimized using both reducing agents. The analy tical performance characteristics of FI-CV-rf-GD-OES for mercury detection were evaluated at the 253.6 run emission mercury line. Detection limits (DL ) of 0.2 ng mL(-1) using SnCl2 and 1.8 ng mL(-1) using NaBH4 were obtained (100 muL sample injections were used). When the optimized experimental cond itions using SnCl2 had been determined, the analytical potential of this CV -rf-GD-OES method was investigated as on-line detector for high-performance liquid chromatographic (HPLC) speciation of mercury (Hg(II) and methylmerc ury). The HPLC-CV-rf-GD-OES detection limits for 100 muL sample injections were found to be 1.2 and 1.8 ng mL(-1) (as mercury) of inorganic mercury an d methylmercury, respectively. The reproducibility observed was below 8% fo r both species. Finally, the HPLC-CV-rf-GD-OES system developed was success fully applied to the determination of methylmercury (speciation) in two cer tified reference materials, Dorm-2 and Dolt-2.