Fiber-optic enzyme biosensor for direct determination of organophosphate nerve agents

A fiber-optic enzyme biosensor for the direct measurement of organophosphat e nerve agents was developed. The basic element of this biosensor is organo phosphorus hydrolase immobilized on a nylon membrane and attached to the co mmon end of a bifurcated optical fiber bundle. The enzyme catalyzes the hyd rolysis of organophosphate compounds to form stoichiometric amounts of chro mophoric products that absorb light at specific wavelengths. The back-scatt ered radiation of the specific incident radiation was measured using a phot omultiplier detector and correlated to the organophosphate concentration. T he effects of buffer pH, temperature, and the units of enzyme immobilized o n the steady-state and kinetic response of the biosensor were investigated to optimize the operating conditions for the fiber-optic enzyme biosensor. These conditions were then used to measure parathion, paraoxon, and coumaph os selectively without interference from carbamates and triazines. Concentr ations as low as 2 mu M can be measured in less than 2 min using the kineti c response. When stored in buffer at 4 degrees C the biosensor shows long-t erm stability.