Determination of metals in solution by chelate formation with intramolecular luminescence-quenched spin-labelled reagents

Chelating reagents whose molecules contain both a luminescent fragment and a spin label near a chelating group are suggested for use in the spectrofluorimetric determination of metal ions. In solutions of such reagents, considerable intramolecular quenching of the fluorescence of the luminescent fragment by the adjacent paramagnetic spin label was observed. The proposed method is based on the change in the degree of luminescence quenching resulting from the alteration of the conformation of the reagent molecule during chelation and a consequent change in the distance between the luminescent group and the spin label. Measurement of the change in the fluorescence intensity of the reagent solution by addition of the metal ions to be determined makes it possible to achieve detection limits of 10^-9 M.