Use of sodium dodecyl sulfate as an antifouling and homogenizing agent in the direct determination of heavy metals by anodic stripping voltammetry.

The effectiveness of the anionic surfactant sodium dodecyl sulfate (SDS) for suppressing adsorption interferences in anodic stripping voltammetry (ASV) was investigated. The samples included fruit juices, wine, beer, milk powder and waste water, and the analytes were cadmium, lead and copper. In most of the samples, the ASV signals were severely depressed or even absent due to electrode fouling, but addition of SDS in concentrations up to 10 g L(-1) proved effective in restoring the ASV response. By using SDS as an interference suppressor, the content of lead and copper in a milk powder reference material was determined, and the results were in agreement with the certified values. In this determination, which could not have been performed without SDS, the surfactant also served as a homogenizing agent, preventing separation of the sample components. The effect of SDS was explained by the interaction of the surfactant with the electrode surface and with the constituents of the sample matrix.