Development of a reactor type bio-sensor for trichloroethylene

This paper describes a microbial sensor for the determination of trichloroethylene (TCE) with flow injection analysis (FIA) based on the microbial degradation of TCE. The sensor consists of two parts, namely, immobilized microbial beads in the column and a chloride-ion electrode as the sensing part. The sensor responds when a change in the concentration of chloride ion is detected as a result of microbial degradation of the TCE in the sample solution. The sensor responded linearly to the TCE in the range of 0.03-2 ppm. The lifetime of a reactor-type TCE sensor is twice that of a membrane-type (microbes immobilized on a membrane) TCE sensor. To avoid the influence of chloride ion in the environment, a dual electrode system was introduced. The reference electrode (chloride-ion electrode 1) measures chloride ion in ground water, while the working electrode (chloride-ion electrode 2) detects chloride ion produced from TCE (as a result of microbial degradation) and that already present in ground water. The difference in the responses of these two electrodes corresponds to the chloride-ion concentration from TCE degradation alone. Two advantages of this sensing system are its simplicity for taking measurements and its ability to avoid influence from any chloride ion already present in the sample solution. This system is more applicable to in situ environmental monitoring than other methods, such as the chromatographic method and a system that we previously constructed in our laboratories.