Precision attainable in the determination of silver by flame atomic absorption spectrometry Analysis of thermoelectric silver-doped tellurides

摘要

Effect of the presence of mineral acids and varied matrix composition were investigated to assess the reliability of flame atomic absorption spectrometric determination of Ag in milligram samples of bismuth antimony telluride monocrystals with thermoelectric properties. For optimum conditions, i.e. hydrogen ion concentration of about 1 mol l~(-1) in a mixture of HNO_3, HCl and tartaric acid, a linear calibration between 0.1 and 3 #mu#g ml~(-1) of Ag was obtained. In order to achieve a high precision of absorbance readings, it was necessary to minimize the time delay (about 2 h for 1 mol l~(-1) of H~+) between the preparation of solutions and the measurements. Under such conditions, a long-run reproducibility of the slope values and reliable determinations of 100-900 #mu#g g~(-1) of Ag in 10-25 mg samples were achieved with relative standard deviation of 1-3%. The 3#sigma# detection limit was estimated to be about 0.050 #mu#g ml~(-1). A modified version of the standard additions technique with three steps was applied to confirm the results close to the limit of determination.