SPECTROFLUOROMETRIC DETERMINATIONS OF CHROMIUM, SELENIUM AND MANGANESE IN THEIR MIXTURES AND THEIR APPLICATION TO ENVIRONMENTAL AND BIOLOGICAL SAMPLES

Highly sensitive and selective fluorimetric methods have been develope d for sequential determination of ultratrace amounts of toxic metals C r, Se, Mn present in mixtures and in biological samples. These are bas ed on a novel oxidative action of Cr(VI), Se(IV) and Mn(VII) on nonflu orescent 2-(alpha-pyridyl) thioquinaldinamide, PTQA, in different acid ic media, i.e., 0.9-0.54 M H2SO4 (for Cr), 0.05-0.15 M H2SO4 (for Se) and 0.033-0.833 M H3PO4 (for Mn) to produce intensely fluorescent oxid ized product of the reagent, having excitation and emission wavelength maximum at 360 and 500 nm respectively. Sequential determination of C r, Se and Mn in their mixtures at different mass ratios have been achi eved with high accuracies. The method has been applied to the environm ental analaysis of biological materials, e.g., aquatic fish samples af ter destruction of organic matter with HNO3-HClO4-H2SO4. The standard deviation for analysis is +/-0.003 for Cr; +/-0.004 for Se and +/-0.00 14 for Mn in mixture while their corresponding values are +/-0.3, +/-0 .3 and +/-0.5 in fish samples. The methods are simple, rapid and highl y reproducible and do not require any cleanup or enrichment step.