Affinity enzymometric assay for detection of organophosphorus compounds

A new method for the detection of organophosphorus compounds has been developed. Organophosphorus compounds are recognized by binding of an excess of bienzyme conjugate (BEC) built up by butyrylcholinesterase as a receptor and horseradish peroxidase as the signal generating and amplifier element. The separation of the analyte-free bienzyme conjugate from the analyte-loaded bienzyme conjugate is performed on an affinity support formed by a Langmuir film containing an amphiphilic paraoxon derivative (B1). The analyte-free bienzyme conjugate binds irreversibly to the affinity support. Bienzyme conjugate with bound analyte is prevented from binding to the B1 film modified support and can thus be detected in the eluate solution by the horseradish peroxidase activity. This activity is directly proportional to the concentration of organophosphorous compounds. The assay procedure was developed for both the steady-state and the flow-injection mode. In both cases the lower limit of detection was about 1 pM for diisopropylflurophosphate.