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

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 mi 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 degrees 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, 3 delta) for cadmium and 9.3 pg (n = 20, 3 delta) for lead. The relative standard deviations based on five measurements for each of the reference solutions (0.25-4.0 mu g Cd2+ l(-1)) and (2.5-40 mu g 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. (C) 2000 Elsevier Science B.V. All rights reserved.