Graphite Furnace Atomic Absorption Spectrometric Determination of Bismuth(III) after Coprecipitation with Hafnium Hydroxide

A method for the coprecipitation of bismuth(III) with hafnium hydroxide followed by a graphite-furnace atomic absorption spectrometric determination is described. Hafnium hydroxide coprecipitates quantitatively 0.05–3 μg of bismuth(III) from 50–400 cm3 of sample solution at pH 5.8–11.2. The presence of 2.5–50 mg of hafnium in 25 cm3 does not affect the atomic absorbance of bismuth(III). The calibration curve is linear for 0.05–3 μg of bismuth(III) in 25 cm3 and passes through the origin. Interference from the presence of large amounts of silver can be eliminated by removing silver as the ammine complex produced by the coprecipitation procedure at above pH 11 with aqueous ammonia. Several other matrix ions investigated do not interfere with the determination in at least a 500-fold mass ratio to bismuth(III). This method was successfully applied to the determination of trace bismuth(III) in commercial metal silver (purity: 99.99%), and is also applicable to the determination of trace amounts of bismuth(III) in water sample