Accurate determination of selenium in the presence of iron by deuterium arc electrothermal atomic absorption spectrometry

Abstract

A method is described which eliminates the over-correction due to spectral interference of iron on the total absorbance of selenium. A pyrolytic graphite platform was pre-treated with 1 mg ml^–1 of platinum and 5% m/v ascorbic acid solution. A 2 µl volume of a 1 mg ml^–1 palladium solution in 4% nitric acid and 0.5% m/v ascorbic acid was used to stabilize and enhance selenium sensitivity. A novel way of simultaneous introduction of palladium and ascorbic acid solutions, without the precipitation of palladium is discussed. Palladium is found to delay atomization of selenium to temperatures of up to 1500 °C. Studies were carried out on 0.6 ng of selenium with varying amounts of iron in the furnace. For an absolute iron content of 40 µg in the furnace, a recovery of 101% was obtained. The method was tested on a solution containing 50 ng ml^–1 of selenium in the presence of 2.5 mg ml^–1 of iron. The standard additions method was used to analyse the solution. A characteristic mass of 25 pg was obtained.