Extraction—spectrophotometric and fluorimetric determination of thallium with 2-(4-methoxyphenyl)-5,7-diphenyl-4h-l,3,4-thiadiazolo[3,2-α] pyridinium chloride

The synthesis, characteristics and applications of 2-(4-methoxyphenyl)-5,7-diphenyl-4H⁺-1, 3,4-thiadiazolo3,2-α]pyridinium chloride (TDZP) as a reagent for the formation of ion-pair complexes is described. Tetrachlorothatllate(III) can be extracted into isoamyl acetate as an ion-pair with TDZP. Thallium can be determined spectrophotometrically and fluorimetrically in the range 1–25 and 0.1–2 μg of thallium per 5 ml of organic layer, respectively. The molar absorptivity is 3.9 × 10⁴ l mol^-1 cm^-1. The quantum efficiency of the reagent is 0.42. The method is applicable to the determination of thallium in sphalerites and zinc or cadmium concentrates.