Speciation of selenium (IV) in natural waters by solid phase spectrophotometry

A method for the speciation of selenium (IV) based on solid-phase spectrophotometry (SPS), has been developed. In acidic conditions selenium (IV) oxidizes potassium iodide and the I(3)(-) forms an ionic association with Rhodamine B (RB) which is fixed on a dextran type lipophilic gel. The gel phase absorbances at 590 and 800 nm are measured directly, and allows for the determination of selenium (IV) in the range of 0.7-18.0 microg l(-1), with a relative standard deviation (RSD) of 2.8%. The method has been applied to the determination of Se(IV) in natural waters.