Voltammetric detection of leadii and mercuryii using a carbon paste electrode modified with thiol self-assembled monolayer on mesoporous silica SAMMS

The anodic stripping voltammetry at a carbon paste electrode modified with thiol terminated self-assembled monolayer on mesoporous silica SH-SAMMS provides a new sensor for simultaneous detection of lead Pb2 and mercury Hg2 in aqueous solutions. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the stripping analysis. Factors affecting the performance of the SH-SAMMS modified electrodes were investigated, including electrode activation and regeneration, electrode composition, preconcentration time, electrolysis time, and composition of electrolysis and stripping media. The most sensitive and reliable electrode contained 20 SH-SAMMS and 80 carbon paste. The optimal operating conditions were a sequence with a 2 min preconcentration period, then a 60 s electrolysis period of the preconcentrated species in 0.2 M nitric acid, followed by square wave anodic stripping voltammetry from −1.0 V to 0.6 V in 0.2 M nitric acid. The areas of the peak responses were linear with respect to metal ion concentrations in the ranges of 10–1500 ppb Pb2and 20–1600 ppb Hg2. The detection limits for Pb2and Hg2were 0.5 ppb Pb2and 3 ppb Hg2after a 20 min preconcentration period.