Fluorescence spectroscopic investigation of the interaction between triphenyltin and humic acids

The interaction between triphenyltin (TPT) and humic acid (HA) was investigated using UV–vis and fluorescence spectra techniques. The experimental results showed that the fluorescence quenching of HA by TPT was a result of the interaction of TPT with HA. The binding constant Kb and corresponding thermodynamic parameters were measured at different temperatures. The binding of TPT molecule to HA is a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. Hydrophobic interaction force plays a major role in stabilizing the TPT–HA complex. The three-dimensional fluorescence contour spectra revealed that TPT could enter into the hydrophobic cavities in some domain of HA.

Humic acid has two fluorescence bands in the fluorescence spectra, which correspond to two different fluorophores that come from different species of humic acid. When different concentration of triphenyltin was titrated into humic acid solution, a remarkable fluorescence decrease of humic acid was observed. The triphenyltin could enter into the hydrophobic cavity in some domain of humic acid.Figure optionsDownload as PowerPoint slideResearch highlights▶ This is the first report on the interaction of triphenyltin with humic acid by fluorescence spectra techniques. ▶ The hydrophobic interaction might play a major role in the binding of triphenyltin to humic acid. ▶ The three—dimensional fluorescence contour spectra revealed that triphenyltin could enter into the hydrophobic cavity in some domain of humic acid.