DETERMINATION OF LEAD AT LOW CONCENTRATIONS IN FOOD SAMPLES BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method for the determination of Pb in biological materials by electr othermal 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 emplo yed. As the contents of Pb in most biological materials are near the l imit of detection, peak height measurement and the method of standard additions were used. The validity of the method was tested using the f ollowing ARC/CL-coded reference materials: wheat flour, potato powder, milk powder and animal muscle, in addition to various other commercia l reference materials. Recovery tests were made on some reference mate rials. The accuracy of the method was satisfactory for the tested mate rials. High lamp intensity and the most sensitive Pb wavelength result ed in better characteristic masses; the characteristic mass in peak he ight mode at 283.3 nm with a hollow cathode lamp was usually 5-8 pg an d at 217.0 nm with the Superlamp, 3-5 pg, depending on the sample matr ix. Low backgrounds were measured in the sample materials. Ammonium ph osphate cannot be employed as the chemical modifier when using the 217 nm line, as phosphate species cause spectral interferences at that wa velength.