CHEMICAL AMPLIFICATION METHOD BY SPECTROPHOTOMETRY FOR THE DETERMINATION OF TRACE AMOUNTS OF SELENIUM

A rapid and sensitive spectrophotometric method has been developed bas ed on the extraction of the ion-association complex formed between ICl 2- and Rhodamine 6G+ into benzene. The ICI2- is formed through iodine which is liberated during the oxidation of iodide by the selenium (IV) present in sulfuric acid medium. The method is sensitive and down to 0.1 mug selenium could be determined in an aqueous phase volume of 10 ml. The extracted Rhodamine 6G+ -ICl2- complex has a molar absorptivit y of 4.8 x 10(5) dm3 mol-1 cm-1 at 535 nm. Beer's law is obeyed over t he range 0.1 to 0.9 mug of selenium. The relative standard deviation i s 2.4%. The method is made more sensitive and selective by adopting th e aluminium hydroxide collection procedure. The interference of few io ns such as Fe3+, VO3-, TeO3(2-) and Sb5+ which were collected along wi th selenium on aluminium hydroxide, were overcome by adding proper mas king agents. The method was applied to the determination of selenium i n environmental ash sample, copper ore, bark sample, and shampoo prepa rations.