Square wave anodic stripping voltammetry: Determination of trace metals in aqueous extracts of soil samples

Abstract

Experiments were conducted using square wave anodic stripping voltammetry (SWASV) to assess the suitability of the method for analysing trace metals from soil samples. Preliminary evaluation indicated that the technique was influenced by factors such as ionic strength (U) of the solution, type of metals and deposition time used, presence of organic acids and the nature of background ionic media. Changes in U, for example, resulted in shifts in peak heights, as well as peak potentials, while long deposition times (>1, 800 s) tended to enhance the sensitivity, resulting in a detection limit of 10-11 M for Cu. The presence of maleic acid and Zn in test solutions gave positive interferences using SWASV. The effect of complexation between metals and several organic acids was elucidated by first determining labile metal concentrations using a background ionic medium of 1 M NaCI, followed by 3 M HCl (PH-0). Since the amount of metals recovered in the presence of HCl was not only higher than in NaCl, but also similar to that determined by atomic absorption spectroscopy, SWASV appeared to be an extremely sensitive procedure for the determination of total as well as chemical speciation of trace metals in aqueous extracts of soil samples. © 1993 Taylor and Francis Group, LLC.