Determination of trace quantities of selenium by indirect atomic-absorption spectrophotometry

The selenium(IV)-iodide interaction in acid medium, leading to the liberation of iodine, has been utilized for the indirect determination of selenium by atomic-absorption spectrophotometry (AAS). The iodine is extracted into benzene and subsequently reductively stripped into an aqueous solution of ascorbic acid. After extraction of the resulting iodide as tris(1,10-phenanthroline)cadmium(II) iodide into nitrobenzene, the cadmium content of the organic extract is determined by AAS. Beer's law is applicable up to 0.75 ppm of selenium. The few interferences are readily overcome. The chemical yield in the system is about 80% overall.