Fluorimetric determination of glycine using copper ion complexes with ciprofl oxacin

A luminescent method for determining glycine based on competitive complexation of Cu2+ ions with ciprofl oxacin and an amino acid is proposed. Formation of a Cu2+ complex with a fl uoroquinolone derivative is shown using spectrophotometry. The resulting complex does not have fl uorescent properties, unlike the ligand itself. In the presence of additives of complexing agent ions in a ciprofl oxacin solution, its fl uorescence is quenched. Introduction of glycine (Gl) into the Cu2+–CF system is accompanied by an increase in the fl uorescence signal of free ciprofl oxacin (CF) (λexc = 330 nm, λfl = 450 nm) with an intensity proportional to the concentration of the amino acid. The eff ect of the nature of surfactant micelles on the emission effi ciency of the analytical system is studied. It is shown that, regardless of their nature, surfactant micelles additionally quench the fl uorescence of Cu2+ ion complexes with CF and Gl. Optimal conditions for complexation reactions in the studied systems, as well as for an increase in the intensity of CF intrinsic fl uorescence, are established. It is assumed that the formation of the analytical signal is associated with the fl uorescence of CF, the concentration of which increases in the solution due to the destruction of the unstable Cu2+ complex with CF and the formation of a more stable Cu2+ chelate with glycine. It is shown that the quenching eff ect is maximal at pH 7 in a phosphate buff er solution. Similar eff ects are not observed in an acetate-ammonia buff er solution. A linear dependence of the fl uorescence intensity on the glycine concentration is observed in the range of 5×10-7 – 5×10-4 M. The detection limit is 2×10-7 M.

: luminescence, complexation of copper ions with ciprofl oxacin, glycine, surfactants