A new solid-liquid extraction sampling technique for direct determination of trace elements in biological materials by graphite furnace atomic absorption spectrometry

A new solid-liquid extraction sampling technique with graphite furnace atomic absorption spectrometry is based on the quantitative extraction of the element of interest from the biological powdered samples into a liquid phase of 1 mol l(-1) nitric acid solution. Examinations of the conditions for sample preparation using solid-liquid extraction (i.e. the effect of concentration of nitric acid, sample mass and ultrasonication time on the extraction) have been carried out in order to obtain 100% extraction of cadmium, copper, lead and manganese from powdered biological samples to the liquid phase. 100% of extraction of these metals is successfully carried out using 1 mol l(-1) nitric acid, and separation of solid phase and liquid phase is done by using a centrifuge (20 min, 4000 rev min(-1)). The proposed method is applied to the determination of cadmium and lead at 0.1 mu g g(-1) levels and of copper and manganese at 10 mu g g(-1) levels in powdered biological samples. These analytical results are ascertained by microwave induced nitrogen plasma-mass spectrometry. Detection limits for cadmium, copper, lead and manganese are, respectively, 0.012 mu g g(-1), 0.829 mu g g(-1), 0.082 mu g g(-1) and 0.125 mu g g(-1) in solid samples, when 50 mg of powdered biological samples is extracted in 5 ml of 1 mol l(-1) nitric acid and then 10 mu l of extracted solution is measured. Precisions of the determination (relative standard deviation at five determinations) of cadmium, copper, lead and manganese are 3.4%, 3.1%, 3.9% and 3.1%, respectively.