2-(α-Pyridyl)thioquinaldinamide: a spectrofluorimetric reagent in inorganic trace analysis. Part III. Determination of manganese in industrial and environmental samples

Abstract

A highly sensitive, fairly selective, direct spectrofluorimetric method for the determination of ultratrace levels of manganese is described. The method is based on the selective oxidation of the very weakly fluorescent 2-(α-pyridyl)thioquinaldinamide by manganese(VII) to give an intensely fluorescent oxidation product (λ_ex.= 360 nm; λ_em.= 500 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity, viz., 0.03–0.83 M H₃PO₄, for periods of between 5 min and 72 h. A linear fluorescence-concentration dependence was observed between 10^–5 and 0.7 p.p.m. of manganese. More than 60 cations and anions, present in a large excess, did not interfere. The method was applied successfully to a number of standard samples (alloys, steels, sludges and sediments), environmental waters (inland and surface) and complex synthetic mixtures. The method is very simple and requires no solvent extraction or pre-concentration steps.