J. Electroanal. Chem., 125 (1981)41--51 41 Elsevier Sequoia S.A., Lausanne -- Printed in The Netherlands SENSITIVITY OF AN INTEGRATING DIFFERENTIAL PULSE POLAROGRAPH TO INTERFERING SIGNALS SAM BEN-YAAKOV * and H. GUTERMAN Department of Electrical Engineering, Ben-Gurion University of the Negev, Beer-Sheva (Israel) (Received 29th September 1980; in revised form 27th January 1981) ABSTRACT A model for error response in differential pulse anodic stripping voltammetry in the pres- ence of a deterministic signal is proposed and successfully applied to predict the error in a practical instrumentation system. It is demonstrated that the system is efficient in rejecting 50 Hz and its harmonics, but produces a relatively large error for interfering signals of low frequencies. The sensitivity of the method in the determination of Cd(II) is estimated theoretically and verified experimen- tally for the polarograph studied. INTRODUCTION Electrochemical methods of polarography and voltammetry have great poten- tiality for the determination of a number of dissolved heavy metals [ 1--6]. Anodic stripping voltammetry (ASV), which increases sensitivity by preconcen- trating the metals on the working electrode, has been shown to be applicable for the analysis of heavy metals in the sub-ppb(pg 1-') levels [7--10]. However, the usefulness of the method as an analytical tool for the determination of trace heavy metals depends on many chemical, physical and operational considera- tions. Among these, the question of sensitivity is central, since the base-line con- centration of dissolved trace heavy metals, such as Zn, Cd, Pb and Cu, in natural waters is very low [8]. A number of methods have been proposed to increase the sensitivity of ASV. Improved pulse technique [ 3,8] and base-line subtraction [ 9,10] are but two examples of the many approaches that have been examined in an attempt to improve the sensitivity of the ASV technique. However, since the ASV signals, like any signal which represents electrical or physical quantities, are invariably accompanied by noise, the ser/sitivity of any ASV technique is ultimately limited by the signal-to-noise ratio. The noise sources can be external noise, such as power-line interference, electronic noise or electrochemical noise, gen- erated at the interface [11--13]. Once the nature of the noise and the interfer- * To whom correspondence should be addressed. 0022-0728/81/0000--0000/$02.50 © 1981 Elsevier Sequoia S.A.