Molecularly imprinted polymers and infrared evanescent wave spectroscopy. A chemical sensors approach

First steps toward a novel chemical sensor based on a molecularly imprinted polymer as the recognition element and infrared evanescent wave spectrosco py as transduction principle are presented. Noncovalently imprinted polymer layers selective for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) have been prepared on the surface of zinc selenide attenuated total reflect ion elements. Selective and reversible binding of the template to the impri nted polymer could be observed on-line by Fourier transform infrared (FT-IR ) spectroscopy. Control experiments were performed with nonimprinted refere nce polymers and with a structurally related compound. The obtained selecti vity data correlate well with those previously obtained with molecularly im printed polymers using radioligand binding assays. This demonstrates the po tential for constructing stable and selective sensors for low-molecular-wei ght organic substances based on FT-IR spectroscopy. Moreover, FT-IR spectro scopy is demonstrated to be a valuable tool for deeper investigation of the binding mechanism in molecularly imprinted polymers.