Application and evaluation of an automatic graphite probe atomiser for the control of vapour-phase interferences in electrothermal atomisation atomic absorption spectrometry

Abstract

Excitation temperature calculations based on the two-line absorption method have indicated that a graphite probe cools the vapour when inserted into a hot atomiser tube. As a result, vaporisation from a probe does not occur under isothermal conditions. However, this does not inhibit the ability of probe atomisation to provide freedom from vapour-phase interferences over a wide range of chloride salt concentrations, provided a high atomiser temperature is selected to minimise the influence of the cooling effect of the probe. At 2700–2900 °C, quantitative recoveries of sub-nanogram amounts of Mn and Pb were achieved in the presence of 35 µg of NaCl, and 10 µg of CoCl2, CuCl2 or MnCl2, respectively. A lower tolerance to chloride interference was observed for Ga, an element that forms a more stable monochloride than either Mn or Pb.Application of the new Philips Analytical PU 9385 autoprobe with the PU 9390 graphite furnace allowed the accurate determination of Cu, Mn and Pb in National Bureau of Standards (NBS) spinach [standard reference material (SRM) 1570] and river sediment (SRM 1645). Aqueous calibration standards and peak-area absorbance measurements were used.