A spectrofluorimetric method for the determination of small amounts of sulphate ion

Abstract

The enhancement of the fluorescence of the binary complex of zirconium with Calcein blue at pH 1·9 is used to determine sulphate ion in the range 0·2 to 12 mg (2 to 12 000 p.p.m.). Excitation and fluorescence maxima occur at 350 and 410 nm, respectively. The fluorescence is stabilised immediately and remains unchanged for over 4 hours. Fluoride present in low concentrations gives rise to high results and must be absent. Other anions that form complexes with or precipitate zirconium, e.g., oxalate, phosphate, tartrate and tungstate, cause low results, but there is a high tolerance towards most cations except iron(III) and cobalt(II).