SQUARE-WAVE ANODIC-STRIPPING VOLTAMMETRY AT GLASSY-CARBON-BASED THIN MERCURY FILM ELECTRODES IN SOLUTIONS CONTAINING DISSOLVED-OXYGEN

Square-wave anodic stripping voltammetry (SWASV) of nanomolar concentration levels of lead and calcium at glassycarbon-based thin mercury film electrodes was investigated in the presence of dissolved oxygen. Anodic stripping measurements in nondeaerated solutions were possible because of the depletion of oxygen at the electrode surface prior to the stripping step and because of the fast-scanning ability of square-wave voltammetry, which allows for the completion of the stripping step before any significant oxidation of the amalgam by diffusing oxygen can occur. Similar measurements by differential pulse anodic stripping voltammetry are not possible unless oxygen is removed from solution. Thin mercury films showed good stability in the presence of dissolved oxygen. Linear calibration curves were obtained for lead and cadmium in acidic media (HCI and acetate buffer, pH 4.8), with no significant loss in stripping current sensitivity due to dissolved oxygen. The SWASV method was successfully used for the determination of lead in untreated, air-saturated tap water samples containing added 0.01 M HCl. The determinations by SWASV agreed very well with the results obtained by electrothermal atomic absorption spectrophotometry. With the time-consuming solution purging step absent and the very fast stripping step, the deposition step is the only time-limiting factor of the method. © 1990, American Chemical Society. All rights reserved.