DETECTION OF HALOGENATED HYDROCARBONS BY A MICROBIAL SENSORSYSTEM USING A STOP-FLOW-TECHNIQUE

To improve the applicability and efficiency of the microbial assay dev eloped by W. Hutter, J. Peter, H. Swoboda, W. Hampel, E. Rosenberg, D. Kramer, and R. Kellner (1995) a stop-flow-technique was developed for the determination of halogenated hydrocarbons in water samples. Cells of Rhodococcus sp. DSM 6344 were immobilized in alginate beads and pl aced in a stirred flow-through reactor. The time of incubation, the ba cterial cell density and the amount of alginate beads in the reactor o n the response of the system as determined by the drop in EMF was inve stigated. Optimal conditions were achieved with 2 g beads containing a bacterial cell concentration of 0,1 g cells wet wt/g matrix and an in cubation time of 20 min. Calibrations with chlorinated and brominated substrates like ethyl bromide, 1,2-dibromopropane, isobutyl bromide, 1 -chlorobutane and 1,5-dichloropentane showed a non-linear dependence a t low substrate concentrations. The detection limits for ethyl bromide and 1-chlorobutane were estimated as 0.02 mg/l and 0.45 mg/l, respect ively; the relative standard deviation was below 10%. The great advant age of the stop-flow-technique compared to discontinuous measurements can be seen in a simplified handling and an increase of sample capacit y.