Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l −1 HNO 3 and in 1+1 v/v diluted wine using mixtures of Pd(NO 3) 2+Mg(NO 3) 2 and NH 4H 2PO 4+Mg(NO 3) 2 as chemical modifiers. With 5 μg Pd+3 μg Mg as the modifiers and a two-step pyrolysis (10 s at 400°C and 10 s at 600°C), the formation of carbonaceous residues inside the atomizer was avoided. For 20 μl of sample (wine+0.056 mol l −1 HNO 3, 1+1, v/v) dispensed into the graphite tube, analytical curves in the 0.10–1.0 μg l −1 Cd and 5.0–50 μg l −1 Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 μg l −1 for Cd, 0.8 μg l −1 for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 μg l −1 and for Pb at 500 μg l −1. The relative standard deviations ( n=12) were typically