SYSTEMATIC STUDIES ON THE DETERMINATION OF GERMANIUM BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY INCLUDING LIQUID SAMPLE INTRODUCTION AND HYDRIDE TECHNIQUES

For the determination of Ge by electrothermal atomic absorption spectrometry the largest enhancement of the Ge absorbance signals and improved reproducibility were obtained with atomisation from a pyrolytic graphite platform using Pd nitrate or Pd nitrate - Mg nitrate chemical modifiers. The characteristic mass found for the integrated absorbance signals in nitric acid and alkaline solutions was about 30 pg of Ge per 0.0044 A s. A relative standard deviation (RSD) of 1-3% was obtained for 1-ng samples of Ge. Atomisation from the wall of a pyrolytic graphite coated graphite tube gave a lower precision and the Ge signals generally decreased after a relatively low number of firings. Hydride generation techniques were combined with the direct introduction of germanium hydride into the graphite furnace and trapping by thermal decomposition. This in situ deposition of Ge was achieved after the Pd [Pd(NO3)2] or Pd - Mg [Pd(NO3)2 - Mg(NO3)2] modifiers (pre-treatment temperature 1100-1200°C) had been deposited on the pyrolytic graphite platform or on a piece of graphite foil at temperatures of 700-800°C. At a recovery of 80-90% the characteristic mass was about 40 pg of Ge per 0.0044 As. The RSD for 1-ng samples of Ge was about 3% for the Pd and 2% for the Pd - Mg modifier. The detection limit was 30 pg of Ge in terms of absolute analyte mass and 3 ng l-1 of Ge in terms of concentration in the buffered sample volume (10 ml) of the hydride generator.