Preparation of an organic acid-imprinted resin by a surface imprinting method.

preparing a resin to recognize a target molecule,1 since it needs no precise design for preparing host compounds (supramolecules), such as crown ethers, cryptands, and cyclodextrins. Many imprinted resins have been prepared as sensors2 and for separating herbicides3 and enantio-isomer compounds.4 We have successfully prepared imprinted resins by a surface imprinting method for metal-chelation using oleic acid5 and phosphoric acid6,7 as a functional surfactant; they were also prepared for catching inorganic anions, such as ferrocyanide8 and condensed-phosphate,9 by using oleylamine. Since this method produces spherical micro-particles, grinding and sieving of the resultant resin are not necessary. In addition, imprinted sites exist on the surface of the resin, so that rapid separation may be achieved. We investigated the preparation of organic acid-imprinted resins by the surface imprinting method. There are many organic acids in foods, especially in vegetable, fruits and fermented foods. The quantitative analysis of organic acids is important for managing food quality, as quantity of the each organic acid in foods is related to the characteristic taste. Among many organic acids, we selected dicarboxylic acids such as phthalic, hexahydrophthalic and 2,3-pyridinedicarboxylic acids as the template, although these acids do not exist in food. Figure 1 shows the concept of organic acid-surface template polymerization in a schematic manner. The functional surfactant monomers and the target organic acid interact with each other at the oil/water emulsion interface. Thus, the organic acid-amino groups complex is immobilized by the polymerization of divinylbenzene as the matrix monomer. The adsorption was investigated for phthalic, hexahydrophthalic and 2,3-pyridinedicarboxylic acids on their imprinted resins and compared to a reference resin (i.e., non-imprinted resin), although the phthalic and hexahydrophthalic acids adsorbed 943 ANALYTICAL SCIENCES AUGUST 2002, VOL. 18 2002 © The Japan Society for Analytical Chemistry