Interference-free determination of selenium in the presence of iron using a graphite furnace with carbon monoxide-platinum modification

Abstract

A method is described which eliminates the spectral interference currently attributed to iron, during the determination of selenium. Carbon monoxide was used as an auxiliary gas at a flow-rate of 0.1 l min^–1 to remove oxygen from the furnace. This prevented the formation of iron oxide which had been previously shown to be implicated in causing spectral interference. Matrix modification was performed by pre-treating the pyrolytic graphite platform with a 1%m/V platinum solution. Studies were carried out with aqueous solutions containing 70 ng ml^–1 of Se, with Fe concentrations varying from 50 to 2000 µg ml^–1, Recoveries ranged from 98.0 to 104.7%. Further studies were carried out on solutions containing 100 ng ml^–1 and 200 ng ml^–1 of Se and varying Fe concentrations. The method of standard additions was used to analyse these solutions. The procedure is rapid, simple and allows the use of deuterium-arc background correction during the determination of Se in water. Previously it was thought that a Zeeman-effect or Smith-Hieftje background correction system was required.