Fluorimetric determination of cerium with oxine-5-sulphonic acid

A simple, sensitive and selective method for the fluorimetric determination of cerium, based on the oxidative reaction between cerium(IV) and oxine-5-sulphonic acid, has been developed. The fluorescent species is an oxidation product of the non-fluorescent reagent and has excitation and emission maxima at 370 and 480 nm, respectively. In the acidity range 1.5 M H2SO4 to pH 1.5, the fluorescent intensity is linear over the range 10 p.p.b.-3 p.p.m. Ce(IV). About fifty cations and anions (including many strong oxidizing agents) show negligible interference effects, even when present in very large amounts. The positive interference of manganese(VII) can be easily overcome by extraction with tetraphenylarsonium chloride in chloroform. Fluoride ion quenches the fluorescence. The method has been applied to the determination of cerium in synthetic mixtures and alloys and ores. Fluorimetric methods for cerium based on the determination of cerium(IV) have not been reported previously