Trace detection of mercury(II) using gold ultra-microelectrode arrays

The electroanalytical detection of trace mercury(II) at gold ultra-microelectrode arrays is reported. The arrays consist of 256 gold microelectrodes of 5 mu m in diameter in cubic arrangements which are separated from their nearest neighbor by 100 mu m. The array was utilized in nitric acid using linear sweep voltammetry where a linear response from mercury additions over the range 10 mu g L-1 200 mu g L-1 (10(-8) - 10(-6) M) was observed with a sensitivity and detection limit of 0.11 nC/mu g L-1 and 3.2 mu g L-1 (16 nM) respectively from using a deposition time of 30 s at - 0.2 V (vs. SCE). This methodology was explored in 0.1. and 1 M chloride media over the mercury range 10 mu g L-1 - 200 mu g L-1 (5 x 10(-8) - 10(-6) M) where similar sensitivities of 0.087 nC/mu g L-1 and 0.078 nC/mu g L-1 were observed with an identical detection limit. The protocol is demonstrated to be useful for the determination of mercury for analysis of environmental water samples.