A Sensor for In-Situ Detection, Identification, and Quantification of TCE for Cone Penetrometers

40765 November 13, 1996 Detection Limit, Inc. Cone Penetrometry, when coupled with a chemical analysis capability, is a powerful method for subsurface mapping of contaminants. However, the fluorescence techniques used to get the qualitative and quantitative chemical information do not have the ability to detect such nonfluorescent materials as chlorinated hydrocarbons. This project will develop a sensor, based on characteristics of laser light scattered from material surfaces, called Surface Enhanced Raman Scattering (SERS), to detect these contaminants. SERS is sensitive only to the layer of contaminants in close proximity to the sensor. The quantity and type of molecules at the sensor is controlled through the use of very specific affinity coatings. This feature, in combination with SERS fluorescence quenching, avoids potential interference from humic or other fluorescence materials. SERS can be performed with a low power diode laser, whereas fluorescence requires a tunable or pulsed source. The near-infrared excitation and the Raman scattered light can be efficiently transmitted to and from the cone head sensor with conventional fiber optics. Anticipated Results/Potential Commercial Applications as described by the awardee: Direct commercial applications are expected in the area of ground contamination mapping using cone penetrometers. The technique could also be used for drinking water, waste water or process monitoring for chlorinated materials.