an electrochemical sensor based on a carbon paste electrode modified with novel nanostructure modifier

Currently, there is an increasing demand to selectively sense heavy metal ions such as hg(ii), cd(ii) and pb(ii) due to their toxic effect on human health [1,2]. among them, mercury is one of the most widely studied toxicant [3]. even a trace amount of mercury intake can lead to serious central nervous system problems and damage vital human organs [4]. therefore, it is of great importance to determine hg in a varied range of samples especially water resources. in the present study, n and s doped carbon/sepiolite nanocomposite was prepared via a simple hydrothermal method. the electrochemical hg(ii) sensing capability of the prepared modifier was studied with the modification of an inexpensive carbon paste electrode (cpe). differential pulse voltammetry (dpv) was applied for quantitative determinations. the effect of several parameters including solution ph, modifier dosage, accumulation potential and accumulation time on the electrochemical signal of the modified electrode were researched, and their values were determined as 5.0, 6.0% (w/w), 0.7 v and 200 s, respectively. the resulting electrode exhibited a linear relationship towards hg(ii) concentrations ranging from 0.4-0.85 μg l-1. the detection limit was found to be 0.1 μg l-1 (s/n = 3) that is lower than the permitted value of hg(ii) reported by the environmental protection agency limit for drinkable water. the relative standard deviation (rsd) for 7 successive measurements at different electrodes was also found to be 2.5%. the interference studies showed that the several common metal ions (e.g., ag(i), pb(ii), cd(ii), co(ii), ni(ii), zn(ii), cu(ii), mn(ii) and cr(iii)) did not interfere with the quantitative mercury determination. the designed sensor was further utilized for the determination of mercury ions in real water samples with satisfactory results.