Simultaneous determination of Cd and Pb in foodstuffs by electrothermal atomic absorption spectrometry Original Research Article

A method for the simultaneous determination of cadmium and lead in foodstuffs by electrothermal atomic absorption spectrometry (ETAAS) with a transversely heated graphite atomizer (THGA) and Zeeman-effect background corrector is proposed. The samples (0.500 g) were digested to clear solutions with 5.0 ml concentrated nitric acid in a closed vessel microwave oven. Among various chemical modifiers tested, the best recovery and repeatability results were obtained with a 0.5% (w/v) NH4H2PO4 + 0.03% (w/v) Mg(NO3)2 mixture. The pyrolysis and atomization temperatures for the simultaneous determination of cadmium and lead were 750 and 1600°C, respectively. Tests carried out with several individual concomitants were performed and did not reveal significant interference on cadmium and lead atomization. Characteristic masses were 1.46 pg for cadmium (RSD = 4.0%) with 8.0% for reproducibility and 36.7 pg for lead (RSD = 2.6%) with 2.0% for reproducibility. The detection limits obtained were 0.38 pg (n = 20, 3δ) for cadmium and 9.3 pg (n = 20, 3δ) for lead. The relative standard deviations based on five measurements for each of the reference solutions (0.25–4.0 μg Cd2+ l−1) and (2.5–40 μg Pb2+ l−1) were always lower than 6.0%. The reliability of the entire procedure was confirmed by spike-tests or analysis of certified reference material (CRM) as spinach (No. 1570a) and bovine liver (No. 1577b) from NIST.