Optimization of the simultaneous batch determinations of Bi(III), Hg(II) and Cu(II) at an epoxy-graphite electrode...

An epoxy-graphite tube composite electrode bulk modified with 2-mercaptobenzothiazole was investigated for the simultaneous, batch determinations of Bi(III), Hg(II) and Cu(II) by differential-pulse anodic stripping voltammetry after open circuit preconcentration of the three metal ions. Systematic optimization was studied with respect to resolution and sensitivities of the differential-pulse peaks. The resolution between peaks was quantified and employed in a window diagram approach to choose the best conditions. The developed method gave detection limits of 4.2 x 10(-9), 3.6 x 10(-9) and 9.5 x 10(-8) M for Hg(II), Bi(III) and Cu(II), respectively (S/N = 3; 3 min preconcentration). The conditions whereby simultaneous determinations could be performed in the absence of cross-interferences of the analytes were also examined. Additional selected substances in the sample background were also studied for possible interferences. The developed method was applied to the simultaneous, batch determinations of Bi(III), Hg(II) and Cu(II) in a standard sample and a human hair sample.