Molecularly imprinted polymer gel with embedded gold nanoparticle was prepared on a gold substrate of a chip for a surface plasmon resonance (SPR) sensor for fabricating an SPR sensor sensitive to a low molecular weight analyte. The sensing is based on swelling of the imprinted polymer gel that is triggered by an analyte binding event within the polymer gel. The swelling causes greater distance between the gold nanoparticles and substrate, shifting a dip of an SPR curve to a higher SPR angle. The polymer synthesis was conducted by radical polymerization of a mixture of acrylic acid, N-isopropylacrylamide, N,N'-methylenebisacrylamide, and gold nanoparticles in the presence of dopamine as model template species on a sensor chip coated with allyl mercaptan. The modified sensor chip showed an increasing SPR angle in response to dopamine concentration, which agrees with the expected sensing mechanism. Furthermore, the gold nanoparticles were shown to be effective for enhancing the signal intensity (the change of SPR angle) by comparison with a sensor chip immobilizing no gold nanoparticles. The analyte binding process and the consequent swelling appeared to be reversible, allowing one the repeated use of the presented sensor chip.

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A molecularly imprinted synthetic polymer receptor selective for triazine herbicides was prepared by suspension polymerization, and was applied to the specific solid-phase extraction of simazine, one of the triazine herbicides, from water. The procedure involves the reversed-phase mode operation of the synthetic receptor to retain lipophilic agrochemicals, including simazine, in water, followed by affinity separation based on hydrogen bonding which exhibits selective retention of simazine, eluting the other undesired compounds. The solid-phase extraction yielded a 56 times concentrated simazine solution with a recovery rate of 91%.Analysis of herbicides in environments is one of the most important fields in analytical chemistry. 1 Currently, gas or liquid chromatography is the most common method for analyzing herbicides, and solid-phase extraction (SPE) is often performed for concentrating and purifying analytes in the samples prior to the chromatographic analysis. 2-5 To date, several types of SPE columns have been developed, which can be classified into various categories in terms of analyte-sorbent interactions employed, such as reversed-phase, normal phase and ion-exchange types. Since those systems utilize nonspecific interactions, conditions for washing and extraction have to be carefully determined according to the chemical characteristics of analytes and other impurities in the samples. Affinity-type SPE columns would be advantageous for analyteselective extraction, because the on-off system does not require careful elution conditions. Although antibodies and receptors are normally used for the development of affinity-type SPE systems, they are hardly available, because of poor stability, when organic solvents are used.Molecular imprinting (MI) 6-11 has been recognized as a potentially useful technique to prepare polymer-type synthetic receptors. We have recently reported on a molecularly imprinted polymer receptor that is selective for triazine herbicides. 12,13 The principle in the preparation of triazine herbicideselective synthetic polymer receptors can be summarized as follows (Fig. 1): firstly, a triazine herbicide and methacrylic acid are mixed in an appropriate solvent to form complexes; secondly, ethylene glycol dimethacrylate is added into the solution, and the complexes are crosslinked; and thirdly, subsequent removal of the triazine herbicide leaves behind cavities complementary to the template molecule that are expected to work as selective binding sites. The polymer receptor exhibited triazine herbicide selective affinity in aprotic and less polar organic solvents, while natural affinity molecules, such as receptors and antibodies, do not exhibit the best performance under such conditions. Accordingly, the molecularly imprinted synthetic receptor could be a good alternative for the natural affinity molecules. 12,14,15 In this paper, we report on a suspension polymerization to prepare a spherical molecularly imprinted synthetic receptor selective for triazine herbicides, and demonstrate a spe...