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

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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.

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