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Fiber‐Optic Enzyme Biosensor for Direct Determination of Organophosphate Nerve Agents

A fiber‐optic enzyme biosensor for the direct measurement of organophosphate nerve agents was developed. The basic element of this biosensor is organophosphorus hydrolase immobilized on a nylon membrane and attached to the common end of a bifurcated optical fiber bundle. The enzyme catalyzes the hydrolysis of organophosphate compounds to form stoichiometric amounts of chromophoric products that absorb light at specific wavelengths. The back‐scattered radiation of the specific incident radiation was measured using a photomultiplier detector and correlated to the organophosphate concentration. The effects of buffer pH, temperature, and the units of enzyme immobilized on 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 coumaphos selectively without interference from carbamates and triazines. Concentrations as low as 2 μM can be measured in less than 2 min using the kinetic response. When stored in buffer at 4 °C the biosensor shows long‐term stability.