On-line Preconcentration and Determination of Trace Heavy Metals by Sequential Injection-Anodic Stripping Voltammetry Using Bismuth Film Screen-printed Carbon Electrode

An automated on-line preconcentration method was developed for simultaneous determination of Pb(II), Cd(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV) using bismuth film screen-printed carbon electrode (Bi-SPCE). The preconcentration of metal ions was performed with a mini-column of a chelating resin, which was installed on a switching valve in the automated system consisted of a syringe pump, an 8-port selection valve and a switching valve. The laboratory-assembled automated on-line pretreatment system (Auto-Pret ASV system) was controlled by the Visual Basic program written by the authors. The metal ions collected on the resin were eluted with 1 M hydrochloric acid, subsequently transported into the flow cell for on-line deposition of analytes on Bi-SPCE at -1.4 V vs. Ag/AgCl; then the flow of the solution was stopped and the voltammogram was recorded from -1.2 to 0.2 V vs. Ag/AgCl by scanning a potential in the square-wave waveform. Experimental conditions, such as pH of sample, a sample flow rate, an eluent volume and its flow rate were optimized. Under the optimum conditions, the analytical characteristics were studied. In addition, the proposed method was applied to the analysis of water samples.