An on-line system for preconcentration and determination of lead in wine samples by FAAS

A flow injection method has been developed for the direct determination of free available Pb(II) and total Pb content in wine samples. The method is based on the chemical sorption of Pb(II), from pH 7 buffered solutions, on a packed polyurethane foam column, modified by addition of 2-(2-benzothiazolylazo)-p-cresol (BTAC). After this step, lead was directly eluted with a stream of 0.1 mol l(-1) HCl into an air C(2)H(2) flame in which lead was determined by atomic absorption spectrometry. Total lead was analyzed after sample digestion with nitric acid and hydrogen peroxide, being free available lead determined by direct sample on-line preconcentration and elution. The method provides a limit of detection (3sigma) of 1 mug l(-1) lead and relative standard deviation, which varies from 6 to 0.7% for lead concentration of 10 and 500 mug l(-1). Total content of lead in wine samples analyzed varied from 8 to 42 mug l(-1) being obtained free available values of Pb(II) under the limit of detection of the method. Recovery studies on natural wine samples, spicked with inorganic lead, evidenced the remaining capability of ligands, present in the wine, to avoid lead retention on the polyurethane foam loaded with BTAC.