AN ABSORPTION-BASED OPTRODE FOR AROMATIC HYDROCARBON DETECTION

REMOTE FIBER SPECTROSCOPY COUPLED WITH FIBER OPTIC CHEMICAL SENSORS HAS SHOWN PROMISE FOR GROUNDWATER MONITORING. LASER-INDUCED FLUORESCENCE HAS BEEN PRINCIPAL DIAGNOSTIC TECHNIQUE INVESTIGATED FOR THE MEASUREMENT OF ORGANOCHLORIDES AND OTHER COMMON GROUNDWATER CONTAINMENTS. LABORATORY AND MODEL FIELD TESTS HAVE INDICATED EXCELLENT SENSITIVITY FOR THESE CHEMICAL SPECIES. EXTENSION OF THIS DIAGNOSITC APPROACH TO AROMATIC HYDROCARBONS AND A PRACTICAL FIELD SYSTEM, HOWEVER, HAS MAJOR LIMITATIONS. AN ALTERNATIVE FIBER OPTIC CHEMICAL SENSOR APPROACH, BASED ON ABSORPTION PHENOMENA, IS PROPOSED FOR THE MONITORING OF AROMATIC HYDROCARBONS. THE SENSOR WILL CONSIST OF AN OPTICAL FIBER SHEATHED WITH A POLYMER HOST CONTAINING AN AROMATIC HYDROCARBON-SPECIFIC REAGENT. THE USE OF LIGHT EMITTING DIODES OPERATING AT DIFFERENT WAVELENGTHS WILL ALLOW SPECIFIC HYDROCARBONS TO BE MEASURED. PARTS PER BILLION SENSITIVITY IS ANTICIPATED ALONG WITH FAST RESPONSE TIME AND REVERSIBLE CHARACTERISTICS. A FIELD SYSTEM SHOULD BE PRACTICAL AND LOW COST. PHASE I WILL INVESTIGATE CANDIDATE REAGENTS AND POLYMER HOSTS; MEASURE EXTINCTION COEFFICIENTS EQUILIBRATION RATES AND SPECTRA; AND FABRICATE AN OPTICAL WAVEGUIDE FOR CALIBRATION EXPERIMENTS.