A Commercialized, Continuous Flow Fiber Optic Sensor for Trichloroethylene and Haloforms

Purus, Inc. has commercialized a fiber optic chemical Sensor using technology developed by Lawrence Livermore National Laboratory and licensed from The University of California. The basis for the sensor is the development of color within a reagent when exposed to an analyte. The sensor consists of an optrode, reagent delivery and recovery system, fiber optic transmitterreceiver, controller, and display. Reagent is pumped through the optrode. Analyte diffuses across a gas permeable membrane and reacts with the reagent to form a colored product. The colored product is detected by measuring the absorbance of light from a 568 nm diode. Reagents are currently available for TCE and mhalomethanes. Initial reagent chemistry is based on the Fujiwara alkaline pyridine reaction. The optrode contacts only gas streams, but the volatility of the current analytes also allows measurements of aqueous streams, without being affected by aqueous intexferents that are non-volatile. Sensitivity of the sensor has been demonstrated to 5 ppb aqueous solutions and 0.1 ppmv in flowing gas streams. INTRODUCTION There has been increasing concem regarding environmental contamination and the associated health hazards from the extensive use of chlorinated hydrocarbons. These concems as well as increasing regulatory requirements have created extensive environmental remediation and monitoring efforts. Present assessment and monitoring methods are labor intensive and frequently suffer long delays between sample collection, analysis, and reporting. Fiber optic chemical sensors can provide a cost effective, real time, in-situ measurement technique to overcome these difficulties. Purus, Inc. has introduced PurSenseTM, a fiber optic chemical sensor, under license from the University of California. This sensor technology was developed at Lawrence Livermore National Laboratory under the direction of Dr. F.J. Milanovich, and is an outgrowth of research fmt sponsored by the U.S Environmental Protection Agency and more recently by the Department of Energy.* The reagent is based on the Fujiwara* alkaline pyridine reaction with halogenated compounds. PurSenseTM technology has broad applicability limited primarily by product configuration and reagent availability. Some product configurations are shown in Figure 1 along with available reagents. Our initial design of PurSenseTM allows it to be used as an industrial process monitoring device or as a laboratory screening instrument. This sensor configuration is currently undergoing field tests. Construction of a field transportable unit is underway with field testing planned to begin during April 1994. In this paper we discuss the packaging of the system into a commercial unit and review the sensor operation and response to both aqueous and gas mixtures of TCE.