A new biospecific technique for organophosphate assay is described. The designed biosensor contains a ferromagnetic core passivated by an epoxide cover in a high-frequency electrical field. Complexing agent molecule with an 8-hydroxy-quinoline region is covalently bound to the cover and serves for strong fixation of aluminum hydroxide. This composition “Magnosorb” binds with the enzyme butyrylcholinesterase. Such a biosensor has high sensitivity to inhibition by organophosphate pesticides (up to 20–50 ng per ml). Various environment and food compounds can be tested without laborious preliminaries. However, the sensor's ability for inhibition is gradually decreased when the full component is stored, whereas esterase activity is more stable. This phenomenon is called “Functional Disadequacy”, and can be corrected with the help of a “Binary Sensor” technique, in which the sensor is made up of two parts (carrier “Magnosorb” and fresh dissolved enzyme) just before use. The proposed method can be used in broad inspection monitoring of an “Alarm Signal”.