Continuous flow system for lead determination by faas in spirituous beverages with solid phase extraction and on-line copper removal

A continuous flow system for the determination of lead in home made spirituous beverages was developed. The determination was based on the formation of a neutral chelate of the element with ammonium pyrrolidine dithiocarbamate, its adsorption onto a minicolumn packed with sodium faujasite type Y synthetic zeolite, followed by elution with methyl isobutyl ketone and determination by flame atomic absorption spectrometry. Ethanol and copper interfere strongly in the determination and therefore, must be separated prior to the analysis. Copper is removed by precipitation with rubeanic acid, while ethanol is eliminated by rotaevaporation. Sample solutions containing Pb2+ in the concentration range from 5 to 120 mug = l(-1) at pH 2.5 could be analyzed, by using a preconcentration time of 3 min. Preconcentration factors from 80 to 140 were achieved for a sample volume of 6 ml and the detection limit varied from 1.4 to 3.5 mug l(-1), depending on the matrix composition. The relative standard deviations for 60 mug l(-1) Pb was 3.2% (n = 10) and the recovery of spikes (20, 40, 60 and 80 mug l(-1)) added to the samples was estimated within 92-105% range, suggesting that lead can be quantitatively determined in such samples. Determining lead in several samples by an alternative technique further checked the accuracy. Finally, the concentrations of Pb2+ determined in 28 samples of Venezuelan spirituous beverages were in 12.6-370.0 mug l(-1) range, depending on the fermenting material based on different mixtures of agave, raw sugar cane and white sugar. (C) 2004 Elsevier B.V. All rights reserved.