Electrochemical SERS Detection of Chlorinated Hydrocarbons in Aqueous Solutions

An in situ method for the determination of trichloroethylene (TCE), perchloroethylene (PCE), chloroform (CHCl₃), and carbon tetrachloride (CCl₄) in aqueous solution is described. The method is based on ESERS—a combination of electrochemical methods and surface-enhanced Raman scattering (SERS). Electrochemistry prepares the surface of a copper electrode for SERS and concentrates the analyte on the surface. The formation of common reaction products for chloroalkanes and for chloroalkenes prevents unequivocal differentiation within a specific class of chlorinated hydrocarbons. However, spectroscopic selectivity between the chloroalkane and chloroalkene classes is excellent, while differences in electrochemical response provide a secondary means for differentiating analyte class. Sensitivity was found to be: <1 ppm for TCE; 15 ppm for PCE; 15 ppm for CHCl₃; and 10 ppm for CCl₄. Application of the method to groundwater contaminated with TCE has been demonstrated. In combination with a fiber-optic waveguide, the ESERS technique offers potential for remote detection of chlorinated hydrocarbons in groundwater and remediation process streams.