ELECTROCHEMICAL SERS DETECTION OF CHLORINATED HYDROCARBONS IN AQUEOUS-SOLUTIONS

An in situ method for the determination of trichloroethylene (TCE), pe rchloroethylene (PCE), chloroform (CHCl3), and carbon tetrachloride (C Cl4) in aqueous solution is described. The method is based on ESERS-a combination of electrochemical methods and surface-enhanced Raman scat tering (SERS). Electrochemistry prepares the surface of a copper elect rode for SERS and concentrates the analyte on the surface. The formati on of common reaction products for chloroalkanes and for chloroalkenes prevents unequivocal differentiation within a specific class of chlor inated hydrocarbons. However, spectroscopic selectivity between the ch loroalkane and chloroalkene classes is excellent, while differences in electrochemical response provide a secondary means for differentiatin g analyte class. Sensitivity was found to be: <1 ppm for TCE; 15 ppm f or PCE; 15 ppm for CHCl3; and 10 ppm for CCl4. Application of the meth od to groundwater contaminated with TCE has been demonstrated. In comb ination with a fiber-optic waveguide, the ESERS technique offers poten tial for remote detection of chlorinated hydrocarbons in groundwater a nd remediation process streams.