PEAK RESOLUTION IN THE DETERMINATION OF COBALT AND NICKEL BY DIFFERENTIAL PULSE AND ALTERNATING-CURRENT ADSORPTION VOLTAMMETRY

The simultaneous determination of cobalt(II) and nickel(II) by differential pulse adsorption voltammetry and fundamental and second harmonic alternating current adsorption voltammetry was compared in the case of very high element concentration ratios. The measurements were carried out in 0.5 M ammonia buffer-1 x 10(-4) M dimethylglyoxime (DMG) as the supporting electrolyte, employing a semistationary mercury electrode with a drop time of 180-240 s (the long lasting sessile drop mercury electrode) as the working electrode. The accuracy of the analytical procedure was checked by the analysis of the standard reference materials: stainless steel (AISI 321) SRM 121-d and highly alloyed steel (Eurostandard 281-1). The precision, expressed as the relative standard deviation, and the detection limits were also reported for each voltammetric technique. The selectivity of the above-mentioned three techniques was found to increase in the following order: second harmonic alternating current adsorption voltammetry > differential pulse adsorption voltammetry > fundamental harmonic alternating current adsorption voltammetry.