The application of ETAAS to the determination of Cr, Pb and Cd in samples taken during different stages of the winemaking process

Chromium, cadmium and lead were determined in different fractions of the winemaking process such as in grape, pressed pomace, must deposit, deposit of lees, must and wine. Grape, pressed pomace, must deposit and deposit of lees were digested by a high-pressure microwave-assisted digestion system with a mixture of nitric acid and hydrogen peroxide, while for must and wine no special treatment was required. The temperature programs of the graphite furnace were optimised and different matrix modifiers were applied: Mg(NO3)(2), NaVO3 for Cr and NH4H2PO4, Pd(NO3)(2) for Pb and Cd determinations. Mg(NO3)(2) and NaVO3 thermally stabilized Cr and enabled the increase of pyrolysis temperatures up to 1500degreesC. NH4H2PO4 and Pd(NO3)(2) are suitable modifiers for Pb and allowed pyrolysis temperatures up to 800degreesC in grape, pressed pomace and wine samples, 1100degreesC in must samples and 1200degreesC in deposit of lees. The non-specific background absorption of NH4H2PO4 was 1.5-2 orders of magnitude higher than that of the Pd(NO3)(2).