Determination of mercury in hair by square-wave anodic stripping voltammetry at a rotating gold disk electrode after microwave digestion

A simple and reliable method for the determination of mercury in hair on a rotating gold disk electrode using subtractive anodic stripping voltammetry without removal of oxygen is reported. Voltammetric and microwave parameters were optimized to obtain the best analytical results. Parameters such as supporting electrolyte concentration, influence of chloride in the Hg peak, deposition potential, scan rate, accumulation time, rotation rate, square-wave amplitude, and electrode conditioning were studied. Pressurized microwave-assisted digestion of hair, suitable for the accurate voltammetric determination of Hg, was evaluated using six acid mixtures and several time-power programs. Under the optimized conditions, no interference by copper, cadmium, lead, nickel, manganese, iron, or zinc was found at concentrations corresponding to their occurrence in normal hair. A calibration plot between 6,67 and 46,69 μg/L was linear, with r ² better than 0.999. The detection limit for a deposition time of 60 s at 25g, was calculated as 1.92 nM (3σ). Validation of the method was demonstrated with the use of a certified reference sample of hair. Eight real samples of hair (four unexposed children and four exposed persons) were also analyzed.