IN-SITU RAMAN-SPECTROSCOPY OF AZA-ARENES ADSORBED AT THE AQUEOUS SILICA INTERFACE

Raman spectroscopy is used to study the effect of pH on the solute/sor bent interactions and the chemical nature of the adsorbed species at t he aqueous/silica interface for the aza-arenes acridine, quinoline, an d pyridine. The neutral aza-arene is hydrogen-bonded to surface sites in aqueous media in which the pH is above the pK(alpha) of the compoun d. A protonated aza-arene/ClO4- ion pair interacts with surface sites in aqueous solutions in which the pH is below the pK(alpha) of the com pound. These results may be useful in predicting the fate of these env ironmentally significant compounds in groundwater.