ANALYTICA zyxwvut CHIMICA zyxwvutsrqpo ACTA Analytica Chimica Acta 312 (1995) 27-34 Signals ratio method for resolution enhancement in differential pulse polarography and related techniques Zorana Grabarik * 11, Boiidar S. Grabari6 ‘, Miquel Esteban, Enric Casassas zyxwvutsrqpo Department of Analytical Chemistry, University of Barcelona, Au. Diagonal 647, E-08028 Barcelona, Spain Received26 January 1995; revised 28 March 1995; accepted6 April 1995 Abstract An effkient and simple resolution method based on signals ratio in time domain is proposed for differential pulse (DP) polarographic and related techniques. The ratio pseudo-DP polarograms are obtained dividing the multianalyte DP polarogram with individual DP polarograms of a single analyte. Using the same procedure for DP polarograms recorded for calibration diagrams and for DP polarograms of unknown binary mixtures, well resolved ratio pseudo-DP polarograms are obtained. The method is applied to the model binary system of lead and thallium, having approximately 70 mV of DP polarographic peaks separation depending of the medium used. DP polarograms of these two metal ions show significant overlapping which depends on their concentration ratio. The method proposed is able to resolve lead from at least 40-fold excess of thallium, and thallium from at least 20-fold excess of lead at micromolar concentration range with reproducibility better than 5%. Keywords: Differential pulse polarography; Resolution enhancement method 1. Introduction Selectivity and sensitivity are the major problems to be solved in chemical sensing and analysis, and, therefore, a lot of investigations have been dedicated in developing selective and sensitive chemical sen- sors [l-3]. Selectivity in voltammetric sensing is due to the fact that different electroactive species un- dergo reduction (or oxidation) at different electrode potentials, but many analytes might interfere if they have close half-wave (or peak) potentials or if they l Corresponding author. ’ On leave from Faculty of Chemical Engineering and Technol- ogy, University of Zagreb, MaruliCev trg 19, HR-41000 Zagreb, Croatia. are present in large concentration excess over the other component(s) present in the sample. One of the advantages of voltammetric techniques is that differ- ent perturbation signals can be applied to the elec- trode, giving different response signal of different shape, enabling a significant sensitivity and selectiv- ity improvement by shear selection of perturbation/ response signals [4,5]. For example, peak-shaped response signals show better resolution than sig- moidal signals, and, as a consequence, differential pulse, square wave, alternating current, derivative, and other related techniques offer better resolution (and sensitivity) than direct current polarography. The oldest strategy for resolving overlapping po- larographic waves was to use chemical reagents for complexing one component in the mixture, in order 0003-2670/95/$09.50 8 1995 Elsevier Science B.V. All rights reserved SSDI 0003-2670(95)00193-X