ADSORPTION OF CHLORINATED ETHYLENES AT 1-OCTADECANETHIOL-MODIFIED SILVER SURFACES

The adsorption of chlorinated ethylenes at octadecylthiol-modified surface-enhanced Raman spectroscopy (SERS) substrates was examined. It was found that the adsorption could be followed with SERS and the adsorption isotherms could be fit to a Frumkin isotherm. In order to better understand variations in the isotherms between substitutions of the chlorinated ethylenes, an isotherm that utilizes an adsorption parameter analogous to the Hildebrand solubility parameter was developed. The adsorption parameters were found to qualitatively follow the solubility parameters. The detection limits were calculated and range from 2086 ppm for trans-1,2-dichloroethylene to 12.6 ppm for tetrachloroethylene. A linear free-energy relationship was found for the log K, adsorption equilibrium constant, and the log S, aqueous solubility, of these compounds. This relationship allows one to predict the detection Limit for low aqueous solubility organic compounds.