OCTADECYLTHIOLMODIFIED SURFACE ImHANcED RAMAN SPECTROSCOPY SUBSTRATES: A NEW METHOD FOR THE DETECTION OF AROMATIC COMPOUNDS

H A method for detection of aromatic organics in groundwater has been tested. It was found that use of surface-enhanced Raman scattering and an octadecylthiol coating on roughened silver produced a system which could partition the organics out of water into the strongly Raman enhanced region near the silver surface. The selectivity of the method was illustrated with the three isomers of xylene. Sensitivity was tested with benzene and naph-thalene. The detection limits are 7.5 and 2.3 ppm for benzene and naphthalene, respectively. It was found that the calibrations followed a Langmuir-type isotherm at low solution concentrations. Introduction There is a subset of the large number of common organic compounds which appears to be ubiquitous to hazardous waste sites. These include primarily aromatic compounds (benzene, toluene, ethylbenzene, and xylenes) and halo-genated organics (I , 2). These compounds are reported at concentrations exceeding 10 ppm in groundwater near these sites. Current monitoring methods for waste sites involve the removal of samples and laboratory analysis. In the case of volatile organics, there can be considerable loss of sample during and after sample collection through aeration and biodegradation (3). We have been examining methods for in-situ detection of groundwater components with fiber optic probes. In this report we will discuss a new method for detection of organic compounds in water.