Sensors based on accumulation in the polymer

More impressive results were obtained with a competitive amperometric device in 1995 [77]. Morphine (for structure see Chapter 14) was imprinted in an 

A conductometric device for measurement of benzyltriphenylphosphonium ions was developed next [80]. Particles of benzyltriphenylphosphonium chloride-imprinted MAA-EDMA copolymer were held in a layer between two platinum wires using a filter paper. The device was exposed to the analyte in acetonitrile, an AC potential applied and the conductance recorded. The direct measurement principle is based on the enrichment of the analyte, a charged species, close to the electrode. A semi-linear response was observed between 1 mg/1 and 20 mg/1 (Fig. 18.4). In the two latter sensors it was anticipated that the effect of non-specific 

Biomimetic electrochemical sensors based on molecular imprinting 

An approach similar to the amperometric morphine sensor has very recently been described by Kroger et al. [81]. Particles of poly(EDMA-co-4-vinylpyridine) imprinted with 2,4-dichlorophenoxyacetic acid were trapped in agarose on a screen-printed carbon electrode. The sensor was equilibrated in a solution of the template analyte species with a fixed amount of the electroactive competitor homogentisic acid, then the free homogentisic acid was quantified by differential pulse voltammetry. This approach has the advantage of being applicable to non-redox-active species, provided a suitable redox-active competitive probe can be found. 

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