Competitive amperometric morphine sensor based on an agarose immobilised molecularly imprinted polymer

A morphine-sensitive device was constructed based on a molecularly imprinted polymer. The imprinted polymer exhibited recognition properties previously. A method of detection based on competitive binding was used to measure morphine in the concentration range 0.1–10 μg/ml. A morphine concentration of 0.5 μg/ml gave a peak current (by oxidation) of 4 nA. The method of morphine detection involves two steps. In the first step, morphine binds selectively to the molecularly imprinted polymer in the sensor. In the second step, an electroinactive competitor (codeine) is added in excess, whence some of the bound morphine is released. The released morphine is detected by an amperometric method. The advantages of this type of sensor compared to biosensors based on antibodies, enzymes or cells are discussed. This sensor, based on an artificial recognition system, demonstrates autoclave compatibility, long-time stability and resistance to harsh chemical environments.