Binding Studies on Resins Imprinted with ( S )-naproxen
- PDF / 132,986 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 55 Downloads / 183 Views
Binding Studies on Resins Imprinted with (S)-naproxen Yue Hu and Robert A. Orwoll Departments of Applied Science and Chemistry College of William and Mary Williamsburg, VA 23187-8795, U.S.A. ABSTRACT
Resins were prepared in a free-radical polymerization of 4-vinylpyridine and ethylene glycol dimethacrylate in the presence of (S)-(+)-6-methoxy-α-methyl-2naphtaleneacetic acid ((S)-naproxen). Initially (S)-naproxen, the imprinted molecule template, was assembled with the monomer 4-vinylpyridine by non-covalent interactions. After the polymerization, stepwise removal of the template left binding sites that retain complementary specificity and affinity. Binding parameters including the maximum number of binding sites and dissociation constant were calculated from the amount of template removed using a two-site Scatchard equation. The results are typical of other systems reported in the literature. INTRODUCTION Molecularly imprinted polymers (MIPs) are synthetic polymers having tailor-made selectivity for a particular template species. They are prepared by self-assembly with a template bound to a monomer in the presence of a crosslinking monomer. Polymerization of the monomers typically results in a macroporous support with the binding monomer positioned for interaction with the template. After extraction of the template, molecular sites are positioned to readsorb the template. Molecular imprinting has been a very active field since 1990. Although attempts have been made to acquire MIP particles dimensionally and morphologically homogeneous, the heterogeneity in the binding has been a significant problem to date in the synthesis of MIPs. The heterogeneity not only affects MIP’s analytical applications, but also complicates MIP’s characterization. Studying how the template molecule is captured by and released from the MIP during the prearrangement procedure, before the polymerization, and during the extraction procedures will help to better understand the heterogeneity in the binding sites. A known MIP system was used: (S)-naproxen as the template and 4-vinylpyridine as the functional monomer. In an early study using (S)-naproxen as a template, Mosbach et al. [1] prepared MIP by a free radical polymerization followed by crushing, grinding, and sieving to produce packing material for high-performance liquid chromatography (HPLC). They found good retentivity and enantioselectivity. Then between 1997 and 2001 Haginaka et al. studied the similar system but developed a multi-step swelling and thermal polymerization method with water as a suspension medium followed by hydrophilic surface modification techniques to make uniformly sized MIP particles [2]. By their method, the separation factor for the enantioselectivity of (S)-naproxen (1.74) was obtained, an improvement over that of Mosbach (1.65). In this study, we employed Mosbach’s method to synthesize MIP. Washing analysis of the template from the MIPs yielded data for a Scatchard plot [3] and the determination M5.7.1 Downloaded from https://www.cambridge.org/core. Columbia
Data Loading...
