Determination of Equilibrium Constants for Binding of Acridine Orange and Its 10-Alkyl Derivatives to Dissolved Humic Substances by a Fluorescence Quenching Method

Abstract

University,Fluorescence intensities of Acridine Orange and its 10-alkyl derivatives were reduced by the presence of commercial humic acid or dissolved humic substances obtained from river water, seawater and pond water samples. Synchronous changes in the absorption spectra and the virtually unchanged fluorescence lifetime of the 10-dodecyl derivative suggested that the fluorescence quenching could be explained on the basis of a static quenching mechanism, in which the fluorescence dyes were bound to humic substances to form non-fluorescent dye aggregates. Curve fitting procedures for the upwardly-curved Stern-Volmer plots yielded the equilibrium binding constants normalized to organic carbon content. The binding constants at pH 7.0 for fractions eluting at pH 2.4 -7.5 in a pH-gradient chromatographic separation of the aquatic humic substances were larger than those for fractions eluting at pH 8.2-11.4. Some chemical properties of the binding have also been discussed in terms of the electrostatic interaction and/or the hydrophobic interaction.

Investigating the Binding of Acridine, Acridine Orange, and Acridine Yellow G to Humic Acid through Fluorescence Quenching

“…The cuvettes were capped with plastic caps and then sealed with Parafilm. The solutions were allowed to equilibrate in the cuvettes in the dark for 24 h, as was done in the work of Ohga et al, 33 who equilibrated the dye solutions in the cuvettes for 12 h.…”

Effects of pH and electrolyte concentration on the binding between a humic acid and an oxazine dye

“…The interaction with mineral surfaces has been relatively well studied (Ha ¨hner, 2002;Neumann and Gessner, 2002;Rytwo et al, 2002). However, there is very limited information on the binding between dyes and refractory organic matter (Banerjee et al, 1973;Ohga et al, 1990), in spite of the importance that this interaction could have in the environment.…”