Fluorimetric use of morin in the ultra-trace determination of cadmium and its application to sewage sludge analyses

Abstract

A sensitive and fairly selective direct spectrofluorimetric method for the ultra-trace determination of cadmium with morin has been developed. The fluorescent chelate [λ_ex.(max.)= 467 nm; λ_em.(max.)= 537 nm] shows a constant fluorescence intensity over a wide pH range (8.0–9.4). The reaction is instantaneous and the fluorescence intensity remains stable for 45 min. Beer's law is obeyed from 0.5 p.p.b. to 0.8 p.p.m. of cadmium; the stoicheiometric composition of the chelate is 1 : 2 (cadmium : morin). The method has been applied successfully to a number of synthetic mixtures of various composition and to some sewage sludge samples after a short, single clean-up step using an ion exchanger.