Theoretical And Experimental Researches On Barbital Molecular Imprinting Polymers

Barbital(BAR) is a kind of psychotropic drugs, and its main clinical efficacy is antiepilepsy, anticonvulsants, and operation anesthesia. Due to the biological functions which are sedative and hypnotic, the livestock and poultry breeders use the BAR as the drug feed additive to improve their economic efficiency. In order to curb the drug abuse, governments issued that people were forbidden to use the barbiturates as the drug feed additive and these drug cannot be showing out in animal tissues. Thus the detection methods for barbiturates residues were also needed to commit.Molecular imprinting technique can prepare varied molecularly imprinted polymers(MIPs), which exactly matches the spatial structure and binding sites of the imprinted molecule. The MIPs owns specific selective adsorption ability and was applied to many detection fields, such as the drug analysis. The stability and the recognition of BAR-MIPs were determined mainly by the hydrogen bond strength between the imprinted molecules and functional monomers. Thus how to choose the proper functional monomers, solvents, and imprinting ratios has been considered as the key to the synthesis of MIPs with highly specific recognition. The molecular simulation technology not only has the guidance for the preparation of MIPs, but also reduces the cost of testing producing by the grope for the polymerization conditions. Consequently, we simulated and optimized the system of BAR-MIPs above all. The BAR-MIPs was prepared and characterized subsequently through the guidance of theoretical results. The main contents are as follows:On the basis of the density functional theory of M062 X, we performed the interaction processes between the barbital(BAR) and different functional monomers, analyzed the solvation effect, and researched the rebinding properties of BAR-MAA complexes toward BAR and its analogues by Gaussian 09 software. The functional monomers were the methacrylic acid(MAA), acrylamide(AM), 4-vinylpyridine(4-Vpy), 2-vinyl-4,6-diamino-1,3,5-triazine(VDAT), and N,N’-methylenebis- acrylamide(MBAD), respectively. The analogues of BAR were the barbituric acid(BA), pentobarbital(PNT), and 1,3-dimethyl barbituric acid(DMBA), respectively. The calculated results indicated that when the imprinting ratio of BAR-MAA complex was 1:6, its the number of hydrogen bonds was the largest, the bond length was the shortest, the binding energy was the lowest. The acetonitrile was expected to be the best solvent to synthesize the strongest BAR-MAA complex in comparison with the AM, 4-Vpy, VDAT and MBAD. The rebinding property of BAR-MAA complex to BAR was excellent when the BAR, BA, PNT, and DMBA existed all at once.The BAR-MIPs was synthesized by precipitation polymerization under the guidance of theoretical results. The experimental results showed that the selective adsorption of BAR-MIPs for MAA and BAR was the best in comparison with the AM, 4-Vpy, VDAT, and MBAD. The adsorption capacity for BAR-MIPs was the highest when the molar ratio was 1:6 for BAR and MAA. In comparison with the toluene, ethylene glycol, dimethylformamide, dimethyl sulfoxide, and water, the BAR-MIPs synthesized in acetonitrile had good dispersiveness. It presented roughly uniform spherical microsphere and owned an average of 190 nm in partical diameter. The imprinting factor of BAR-MIPs toward BA, PNT, and DMBA were 1.22, 1.29, and 1.81, respectively. Thus, the BAR-MIPs possessed high selective ability for BAR. These experimental results were consistent to the theoretical ones. Furthermore, analysis of the scatchard plot revealed that the maximum adsorption quantity of BAR-MIPs was 17.5 mg/g for high and selective affinity sites. The thermodynamic study implied that the adsorption of BAR-MIPs to BAR was an exothermic process, and the detection sensitivity of BAR-MIPs for BAR drugs was high at the low temperature.The BAR-MIPs was considered as the selective adsorbent material to separate and concentrate the BAR in the spiked pork sample. The results showed that the saturated adsorption capacity of BAR-MIPs to BAR was 9.2 mg/g and the adsorption rate of recovery was 81.52%~91.30%. Thus, the BAR-MIPs can be used to prepare the imprinted adsorbent material in actual samples.