A RAPID FLUORESCENCE QUENCHING METHOD FOR THE DETERMINATION OF EQUILIBRIUM PARAMETERS FOR COPPER(II) COMPLEXATION BY HUMIC MATERIALS

Fluorescence quenching measurements for determining stability constants (K) and complexation capacities (CL) of copper(II) complexation by humic materials have primarily been conducted by titrating a sample with metal ion. These titrations are long and tedious, requiring many data points, pH adjustment between additions, and long equilibration times. Once collected, the data must then be manipulated using regression analyses to obtain the equilibrium parameters. This paper describes the development of a new, rapid method of determining equilibrium parameters from fluorescence quenching. The use of individual pH-buffered aliquots of sample for each point along the titration curve yields data that can be analyzed with a simplified linear data treatment to obtain values for CL and K for the sample. This rapid fluorescence quenching method was evaluated using a model ligand (salicylic acid), isolated soil and stream fulvic acids, and a natural water sample. © 1991.