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Study on the Molecular Recognition Properties of 1-naphthylamine Molecularly Imprinted Polymer and Application of Solid-phase Extraction

Author: TangZuoZuo
Tutor: YangJun
School: University of Science and Technology of China
Course: Analytical Chemistry
Keywords: 1-naphthylamine molecular imprinted polymers molecular recognition solid-phase extraction mainstream tobacco smoke aromatic amines
CLC: O631.3
Type: Master's thesis
Year: 2010
Downloads: 96
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Abstract

In this thesis, the development and application of molecular imprinting technique and the analytical techniques of aromatic amines (AAs) were reviewed in detail. Then a new molecularly imprinted polymer (MIP) with high selectivity and excellent affinity for 1-naphthylamine (1-NNA) was firstly synthesized using 1-NNA as the template molecule. Next, the recognition mechanism between 1-NNA and MAA and the binding affinity of the MIP were studied. Finally, the 1-NNA imprinted polymer was used as the sorbent of solid-phase extraction (MISPE) to testify the feasibility of selectively extraction of Hoffman AAs (2-naphthylamine, 1-naphthylamine, 4-aminobiphenyl and 3-aminobiphenyl) in mainstream tobacco smoke. Primary studies in the thesis are included as following:1. A new molecularly imprinted polymer (MIP) with high selectivity and excellent affinity for 1-NNA based on non-covalent interaction was firstly synthesized using 1-NNA as template molecules, methacrylic acid (MMA) as functional monomers, ethylene glycol dimethacrylate (EDMA) as crosslinker and azobisisobutyronitrile (AIBN) as initiator. UV, IR, XPS and 1H NMR spectrometric methods were adopted to study the interaction and recognition mechanism between 1-NNA and MAA. The results demonstrated that the NNA-MAA complexes of 1:1 mole ratio were obtained by hydrogen bonding and the complexes possessed better stabilization (K=5.537×104L/mol) . Furthermore, nitrogen atom of the amino group in 1-NNA is hydrogen-bond acceptors. Hydrogen atom of the carboxyl group in MMA is hydrogen-bond donor.2. Equilibrium adsorption experiments and Scatchard analysis were used to evaluate the binding affinity of the MIP. In equilibrium adsorption experiments, when the initial 1-NNA concentration is 1.5mmol/L,the imprinting factor (I) is 2.03, suggesting that comparing to non-imprinted polymer (NIP), MIP showed better binding ability to 1-NNA. In Scatchard analysis, an excellent linear relationship was obtained between the B/[1-naphthylamine] and B, suggesting that the binding site can be classified into one distinct group with specific binding property. The equilibrium dissociation constant (KD) value can be calculated to be 0.7845μmol/L, and the apparent maximum number of binding sites (Bmax) 93.4μmol/L. Results of Scatchard analysis demonstrated that the MIP had high affinity and more binding sites for 1-NNA. Selectivity adsorption experiments among structural analogues on MIP were used for evaluation of selectivity. The absorption of 1-NNA is significantly higher than other analogs, indicating that the MIP has high selectivity for 1-NNA. The same selectivity adsorption experiments were carried on NIP, and the data show that for the NIP, the absorption of the substrate is mainly non-specific, while the MIP has a specific adsorption to 1-NNA.3. 1-NNA imprinted polymer was used as the sorbent of solid-phase extraction (MISPE). The conditions of loading, washing and eluting procedures were optimized to testify the selectivity of seven AAs (aniline, o-Toluidine, 2, 6-dimethylaniline, 2-naphthylamine, 1-naphthylamine, 4-aminobiphenyl and 3-aminobiphenyl) standard solution. The results showed that under the optimized conditions, the MISPE offered excellent affinity and high selectivity to the four AAs (2-naphthylamine, 1-naphthylamine, 4-aminobiphenyl and 3-aminobiphenyl), indicating that the absorption of the four AAs is specific. Then the same experiments were carried in tobacco smoke added the four AAs standard solution. The results showed that the extraction recoveries of the four AAs were higher than 80%, indicating that the MISPE can be effective to extract the four AAs from mainstream in complicated tobacco smoke. The same experiments were also performed using blank polymer SPE cartridge (NISPE). Compared to the results obtained with NISPE, it is clear that MISPE can extract the four AAs from mainstream. Standard addition method coupled with MISPE was used to determinate the four AAs in mainstream mix tobacco smoke.

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