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A relationship was derived for the resolution of differential pulse polarography as a function of the pulse amplitude and various parameters of the electrode reaction of the simultaneously present components(number of electrons exchanged in the electrode reaction, half-wave potentials). The resolution was found to be higher at small pulse amplitudes and large difference in the half-wave potentials.Resolution is higher when the number of electrons involved in the electrode reaction of both the measured and the interfering species are larger and it is mainly affected by the latter. The resolution of differential pulse polarography was found to be inferior to that of fundamental harmonic and second harmonic ac. polarography.

The simultaneous determination of cobalt(II) and nlckel(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 dlmethylgtyoxlme (DMG) as the supporting electrolyte, employing a semistatlonary 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.

weight and large size of the ion association molecule. ACKNOWLEDGMENTWe express our deep thanks to .