Highly sensitive determination of mercury using copper enhancer by diamond electrode coupled with sequential injection–anodic stripping voltammetry

Abstract

A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection–anodic stripping voltammetry (SI–ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at −1.0V (vs. Ag/AgCl, 3M KCl) for 150s with a flow rate of 14μLs−1. An anodic stripping voltammogram was recorded from −0.4V to 0.25V using a frequency of 60Hz, an amplitude of 50mV, and a step potential of 10mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at −0.25V and +0.05V (vs. Ag/AgCl, 3M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1–30.0ngmL−1 and 5.0–60.0ngmL−1). The limit of detection (S/N=3) obtained from the experiment was found to be 0.04ngmL−1. The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20ngmL−1, respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg(II), according to the paired t-test at a 95% confidence level.