SONO-ELECTROANALYSIS - APPLICATION TO THE DETECTION OF LEAD IN WINE

The quantitative detection of lead in wine is shown to be possible by anodic stripping voltammetry under conditions of insonation. An immers ion horn probe is introduced into a thermostatted conventional three-e lectrode cell opposite a mercury plated platinum disc working electrod e. Following acidification of the wine sample lead ions can be reduced at the Hg/Pt electrode surface at -1.0 V (vs SCE). The large mass tra nsport associated with power ultrasound yields efficient pre-concentra tion of the lead before it is stripped by an anodic linear sweep of th e potential. Insonation further offers the crucial benefits of first s urface activation and cleaning, helping to prevent electrode fouling b y the organic components in wine and second fully equilibrating ''free '' and ''bound'' Pb2+ ions in the complex matrix. By use of standard m icroaddition of lead to the solution the system can be calibrated to g ive the total amount of lead present. Experiments using samples of a w hite Italian Chardonnay gave a total lead content of 22 +/- 6 mu g l(- 1). This value was compared with those obtained by independent atomic absorption spectroscopy (AAS) measurements performed by two different laboratories. Quantitative agreement was found. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.