Lead determination in ultra micro samples of animal diet using graphite furnace atomic absorption spectrometry

A graphite furnace atomic absorption spectrometry method has been developed for the determination of very low levels of Pb in small samples of animal diet. The method is based on a microwave-assisted pressure vessel digestion using miniaturized vessels for sample masses of 100 mg. Due to the small acid volume, the dilution factor during digestion was only 10. Detection limits of 5 μg/kg Pb were achieved in a complex matrix consisting of mainly caseine 22% (w/w), corn starch 28.6%, sucrose 30%, cellulose 4%, soya oil 7%, minerals 5.2%, vitamins 2%, and DL methionine 0.4%. The reproducibility of the method was 15% at a Pb concentration of 37 μg/kg and 11%, respectively, using the standard additions method before and after digestion. The recoveries of Pb added to the samples prior to or after digestion were 83.2 ± 3.0% and 82.3 ± 2.2%, respectively.