Determination of lead at low concentrations in food samples by electrothermal atomic absorption spectrometry

Abstract

A method for the determination of Pb in biological materials by electrothermal atomic absorption spectrometry was tested at a wavelength of 217.0 nm and with 0.1% Pd as the chemical modifier. A Varian SpectrAA 400 Zeeman spectrometer equipped with a Photron Pb Superlamp was employed. As the contents of Pb in most biological materials are near the limit of detection, peak height measurement and the method of standard additions were used. The validity of the method was tested using the following ARC/CL-coded reference materials: wheat flour, potato powder, milk powder and animal muscle, in addition to various other commercial reference materials. Recovery tests were made on some reference materials. The accuracy of the method was satisfactory for the tested materials. High lamp intensity and the most sensitive Pb wavelength resulted in better characteristic masses; the characteristic mass in peak height mode at 283.3 nm with a hollow cathode lamp was usually 5–8 pg and at 217.0 nm with the Superlamp, 3–5 pg, depending on the sample matrix. Low backgrounds were measured in the sample materials. Ammonium phosphate cannot be employed as the chemical modifier when using the 217 nm line, as phosphate species cause spectral interferences at that wavelength.