Detection of Chlorinated Hydrocarbons in Aqueous Surfactant Solutions by Near-IR Raman Spectroscopy

Near-IR Raman spectroscopy is used to detect chlorinated hydrocarbons under surfactant-enhanced solubilization conditions. The Raman bands of tetrachloroethylene (PCE) and 1,2-dichlorobenzene (DCB) in micelle solutions could be observed in the presence of humic acid when a 784-nm diode laser was used. With 532- or 632.8-nm excitation, humic acid fluorescence obscured the Raman signals. For quantification, the integrated area of the carbon-chlorine stretch mode (PCE) or the phenyl ring-breathing mode (DCB) was used. Test results for samples with unknown concentrations based on linear calibration curves were in agreement with results from an accepted gas chromatography method. Detection limits were calculated to be 240 ppm for tetrachloroethylene and 500 ppm for 1,2-dichlorobenzene. Our study has shown the feasibility of this technique for field applications.