| Abstract: | An optical fiber enzymatic biosensor was formed by immobilizing cells containing atrazine chlorohydrolase to the surface of a pH-sensitive optode. This enzyme catalyzes the dechlorination of atrazine, releasing hydrochloric acid and creating a signal response from the optode that was proportional to the atrazine concentration. Biosensors capable of quantitative and sensitive atrazine concentration measurements were developed using the atrazine chlorohydrolase of both Pseudomonas sp. ADP and Clavibacter michiganese sp. ATZ1. The biosensors based on both bacteria had a limit of detection of less than 1 ppb (validated using gas chromatography) and a linear range from 1 ppb to 100 ppb atrazine. Response times were a function of concentration and the source of enzyme, with a response time of 10 or 20 min for a 25 ppb atrazine solution. The performance of these sensors at various temperatures, pH values, and buffer capacities was also studied. The use of poly-L-lysine to increase the physical stability of biosensors containing Pseudomonas sp. ADP provided higher durability with no performance drawbacks. The atrazine biosensor was also used to measure atrazine concentrations in a soil column that was continuously fed a solution in which the atrazine concentration was increased or decreased. The atrazine biosensor provided continuous, in-situ measurements in the soil column, the first time that continuous biosensor measurements have been demonstrated in a soil system. |
