Evaluation of internal standardisation in electrothermal atomic absorptionspectrometry

Significantly improved performance in electrothermal atomic absorption spec trometry is possible using an internal standardisation technique. A Perkin- Elmer SIMAA 6000 simultaneous multielement spectrometer was used to study t he correlation between two integrated absorbance signals. The behaviour of Pb (analyte) in different urine, blood and placenta samples was compared to that of Bi or Tl used as the internal standards. All samples were spiked w ith known amounts of Pb and Bi or Tl. A satisfactory signal correlation (r = 0.94) between the integrated absorbances for spikes of the analyte and in ternal standard was observed with Bi as the internal standard. After signal correction, the relative standard deviation of the integrated absorbance f or Pb spikes reduced from 29 to 7% for urine, from 19 to 2% for blood and f rom 22 to 4% for placenta. The mean difference between Pb concentration fou nd in analysed samples by the method of additions and using an internal sta ndard was 10%.