Determination of Zn, Cu, Cd, Pb, Ni and Cr in some Slovenian foodstuffs

Abstract

An acid-assisted microwave digestion procedure was optimised for the determination of trace elements in foodstuffs by the use of flame and electrothermal atomic absorption spectrometric (FAAS, ETAAS) techniques. Zn, Cu, Cd, Pb, Ni and Cr were determined in cabbage, wheat, potato, instant milk, fish, eggs and baby foodstuffs. The repeatability of measurements was tested in the cabbage sample and was found to be ±3.3% for Zn, 4.6% for Cd, ±6.8% for Cu and ±15.5% for Cr. The worse value obtained for Cr was probably due to its inhomogeneous distribution and very low concentration in the cabbage. Concentrations of Ni and Pb in the cabbage sample were below the limit of detection (0.2 mg kg−1). The accuracy of the analytical procedure was checked by the analysis of the standard reference material CRM 1570 Trace and minor elements in spinach leaves and IAEA 336 Trace and minor elements in lichen. Good agreement between the certified or indicative and determined values was obtained. The results indicate that the concentrations of Zn, Cu, Cd, Pb, Ni and Cr found in cabbage, wheat and potato are comparable to the literature data. Cd, Pb and Ni were not found to be the contaminants in the foodstuffs analysed. Higher concentrations of Ni were found only in baby food "Cokolesnik", arising from the cocoa that "Cokolesnik" contained. It was demonstrated that the Cr content is very low in baby food, yolk and white of egg and in fish (<0.05 mg kg−1 Cr). Elevated concentrations of trace elements were found only in mussels that accumulate heavy metals from the marine environment.