THIO MICHLER KETONE AS A SENSITIVE SPECTROPHOTOMETRIC REAGENT - SPECTROPHOTOMETRIC DETERMINATION OF PLATINUM

The stability of Thio Michler's Ketone (TMK) in some organic polar solvents has been examined. The reagent is unstable under light exposition and at pH below 5 is oxidized by oxygen from air. The oxidized forms have been identified by means of UV-VIS spectroscopy; they do not appear in TMK solutions stored in a nitrogen atmosphere. As a result of experiments concerning the properties of TMK, the reduced form of the reagent has been proposed as the reactive species with respect to metal ions. The optimum conditions for the formation of a platinum complex with TMK have been evaluated for a variety of mixed aqueous-organic solvent media. As the most sensitive spectrophotometric method for Pt determination, the one based on the PT-TMK complex in a water-ethanol solution has been developed (epsilon = 1.25 x 10(5) l.mol-1.cm-1 at 540 nm). By means of the proposed method the platinum content in a contact of a light-emitting diode has been determined.