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Preparation and properties of chlorogenic acid molecular imprinting system computer simulation and composite membranes

Author: LiXiuFang
Tutor: ZhongShiAn
School: Central South University
Course: Analytical Chemistry
Keywords: molecularly imprinted polymer composite membrane computer stimulation scatchard analysis permeation chlorogenic acid
CLC: TB383.2
Type: Master's thesis
Year: 2011
Downloads: 126
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Abstract

In this paper, there was a combination of way that theoretical calculation and experimental operation. First, doing the comprehensive analysis of the molecular structure of functional monomers and templates were to design and match the structure of the molecules, then it could form a stable polymer pre-assembly systems. It was based on the comparison of binding energy of the complexes between the template and different functional monomers, to select the appropriate functional monomer, to determine the best system of composite molecular imprinting. Then polyvinylidene fluoride microporous membrane as the support membrane, chlorogenic acid as template,4-vinylpyridine (4-VP) as a functional monomer using surface modified polymerization had prepared the chlorogenic acid molecularly imprinted polymer composite membranes. Molecularly imprinted polymer composite membranes could be used for separation and enriching the target molecule of chlorogenic acid in harsh environmental conditions.The main contents are as follows:1. Computational approach using the Hartree-Fock (HF) method and PM3 method, the geometry optimization, energy and binding energy of imprinted molecule with functional monomer were studied by Gaussian 03 soft. Chlorogenic acid is taken as template molecule, and acrylamide (AM), acrylic acid (AA), methacrylic acid (MAA),4-vinylpyridine (4-VP) and 2-vinylpyridine (2-VP) are taken as functional monomer, respectively. The order of the binding energy of chlorogenic acid with the above monomers was discussed, and the highest binding energy is 4-vinylpyridine (4-VP).2. According to the pre-assembly systems which had been determined the template and functional monomer. Under the really synthesized conditions, polyvinylidene fluoride microporous membrane as the support membrane, chlorogenic acid as template,4-vinylpyridine (4-VP) as a functional monomer using surface modified polymerization prepared the chlorogenic acid molecularly imprinted polymer composite membranes. We used scanning electron microscopy and infrared spectroscopy to analyze the prepared molecularly imprinted polymer composite membranes.3. Chlorogenic acid molecularly imprinted polymer composite membrane could remain the basic morphology and structure in hot water, strong acid, strong alkali, other strong chemical corrosion and harsh environment. Binding assays and permeation experiments showed that chlorogenic acid molecularly imprinted polymer composite membrane had two types of non-specific binding sites. The dissociation constant (Kd) of binding sites Kd1=0.151 mmol·L-1 and Kd2=0.480 mmol·L-1, and the maximal apparent bonding constant were 14.934μmol·g-1 and 28.123μmol·g-1. And the combining quantity of was 24.20μmol·g-1, it was 2.40 time of caffeic acid, but the binding capacity of substrate on the composite membrane prepared by different functional monomers showed a lot of difference. Chlorogenic acid molecularly imprinted polymer composite membrane had some specific performance that other polymer materials were not, to the template had superb combination of specific and selective, which played an important role in efficient selection and separation of active ingredients in Chinese herbal medicine. The topics were worth developing and researching, having important commercial value.4. The detection limit of chlorogenic acid using HPLC was low, the rate of the recovery experiment was high. The enrichment experimental studies of Chlorogenic acid molecularly imprinted polymer composite membrane for chlorogenic acid in eucommia leaf had shown that chlorogenic acid molecularly imprinted polymer composite membrane on the accumulation of chlorogenic acid was far stronger than the non-imprinted membrane. Because imprinted polymer composite membrane contained a lot of functional groups which could interact with the template molecule. A large number of three-dimensional cavities were obtained after washing off the template molecules. The shape, size of the cavity was exactly matched with template molecules; rather than the distribution of the functional groups of the non-imprinted polymer composite membrane was chaotic, the degree of the matching was very low. The adsorption and desorption experiments of the molecular imprinted polymer composite membrane also showed that the same conclusion.5. The elution of the solution of the methanol and acetic acid at the rate of the 1:10 for the molecular imprinted polymer composite membrane was best. With the increase of acidity, elution effect is getting worse. The ability of the elution of the methanol and acetonitrile for the template was low. Under the certain acidic conditions,the experiment showed that the specific recognition sites (the functional groups of the functional monomer) and the cavity structure of the molecular imprinted polymer composite membrane could maintain a steady state, the prepared molecularly imprinted polymer composite membrane still could be used for separating and enrichment the target molecule chlorogenic acid under the harsh outside conditions.

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