INVESTIGATION OF AUTOMATED-DETERMINATION OF GERMANIUM BY HYDRIDE GENERATION USING IN-SITU TRAPPING ON STABLE COATINGS IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

Sequestering and in situ concentration of Ge hydride in the graphite f urnace can be automated by using a highly stable trapping reagent to r eplace the Pd modifier, In a systematic study, two groups of trapping reagents which require only a single application, i,e,, carbide-formin g elements (Zr, Nh, Ta or W) and noble metals (Ir, Pd-Ir), were invest igated and trapping temperature curves were measured, It was shown tha t effective trapping of germane is possible on Zr-coated tubes and pla tforms at trapping temperatures of 550-750 and 600-800 degrees C, resp ectively, Trapping temperatures should not exceed 650 degrees C (the ' critical temperature') because at temperatures higher than 650 degrees C errors in absorbance values could occur owing to an adsorptive 'car ry-over effect', Good signal stability was observed over more than 400 complete trapping and atomization cycles, and a precision of better 3 % was obtained, Comparatively small signals were observed for the Nb-, Ta- and W-coatings. Ir-coated graphite tubes allowed trapping of germ ane at lower temperatures (400-500 degrees C) but the signals were sma ll and of low stability, compared with those for the Zr coating, Chara cteristic masses of about 54 pg of Ge on Zr-coated graphite tubes (pea k height) and 108 pg of Ge on Zr-coated platforms (integrated absorban ce) were observed, and the calibration graphs were linear up to 4 ng o f Ge on both tubes and platforms,The detection limit was 18 pg of Ge f or a 1 ml sample volume using flow injection hydride generation, The m ethod was tested by applying it to the determination of Ge in sediment , geological and low-alloy steel certified reference materials.