Photometric determination of selenium with ferrocene

A sensitive spectrophotometric method for the determination of selenium has been developed. The method depends on a redox reaction between selenious acid in 8M hydrochloric acid and a chloroform solution of ferrocene. One mole of selenious acid produces 4 moles of ferricenium ions, which are then oxidized by bromine water. The resulting iron(III) is reduced to iron(II) and determined with 1,10-phenanthroline. The relative standard deviation for 20 mug of selenium was 1.1%. The apparent molar absorptivity of the final solution, referred to selenious acid, is 4.23 x 10(4) 1. mole(-1). cm(-1) at 512 nm. This method has been used to determine selenium in copper metal.