| Abstract: | Liquid chromatography with pulsed amperometric detection (PAD) at an Au electrode was successfully applied for speciation of mercury: inorganic mercury, methylmercury and ethylmercury. The optimized conditions for triple-step potential waveforms utilized in PAD were: E1 1800 mV, t1 50 ms; E2 300 mV, t2 3850 ms; E3 750 mV, t3 100 ms; mercury oxidation was monitored at E3. With the eluent of HClO4 (0.10 M) + KCl (1.0 mM) + CH3CN (1.0%) at a flow rate 0.80 mL/min, three mercury species were fully separated in 6 min on a glass column (3 mm × 10 cm) packed with Chemcosorb C18 (5 μm). However, the first peak (inorganic mercury) was commonly overlapped by the solvent front. The relative standard deviations (n = 6) for methylmercury (15 ppb) and ethylmercury (30 ppb) were 4.2% and 2.8%, respectively. The linear range tested was 2 – 500 ppb (r = 0.9998) for methylmercury, and was 4 – 1000 ppb (r = 1.000) for ethylmercury. The detection limits (S/N = 3) were 1.2 ppb and 1.8 ppb for methylmercury and ethylmercury, respectively. The results of determination of the mercury-containing species thimerosat in three commercial contact-lens solutions agreed satisfactorily with the expected values. |
