| Small molecular toxins existing in food can be easily separated and purified with molecularly imprinted solid phase extraction application in food analysis. In the study tyramine and 3-Nitropropionic acid molecularly imprinted polyer were synthesized, the characteristics were studied, and the desired functional polymer were applied for determination of them in food analysis, the details are as follows:Quantization calculations were carried out by using Gaussian software based on the application of Hartree–Fock(HF) method with 6-31G(d) basis set. A virtual library of functional monomers i.e. methacrylic acid(MAA), acrylic acid(AA), p-vinyl benzoic acid(P-VBA) and methyl methacrylate(MMA) were used to assign and screen against the target template molecule, and managed to improve the selectivity of MIP with the computer simulation based on the comparison of the binding energy(△E) of the formed complexes between the template molecule and different functional monomers. The theoretical calculation results showed that among these functional monomers used in this work, MAA and P-VBA gave the largest △E which means greater interaction and the optimal template-monomer complexes molar ratio is 1:3. The above mentioned work made the more selective tyramine molecularly imprinted polymer possible.Tyramine molecular imprinted polymer(MIP) was prepared by precipitation polymerization using tyramine, p-vinylbenzoic acid(P-VBA), ethylene glycol dimethacrylate(EGDMA), azobisisobutyronitrile(AIBN), and acetonitrile as template, functional monomer, cross-linker, initiator and porogen, respectively. The UV spectrophotometry and NMR were used to demonstrate the interaction between tyramine and P-VBA. The adsorption characteristics of MIP to tyramine were studied by equilibrium binding experiment and Scatchard analysis. The data obtained showed that MIP reached absorption equilibrium within 2 h. The Scatchard chart showed the apparent maximum binding capacity(Bmax) and the dissociation contents(KD) of MIP were 337.31 μmol/g and 0.15 mmol/L, respectively. The specificity and selectivity of the obtained imprinted polymers were investigated by binding analysis using tyramine and tyramine analogues. The results indicated that the obtained imprinted polymers showed a good selectivity and specificity adsorption to tyramine.To establish a method for determination of tyramine in soy sauce by molecular imprinting solid phase extraction(MISPE) and high performance liquid chromatography(HPLC). Tyramine molecularly imprinted polymer(MIP) was prepared by bulk polymerization, the prepared MIP was used as filler to make MISPE column. The extraction conditions for tyramine were optimized before HPLC determination. The optimized conditions were as follows: the loading, washing, eluting solvent was 5% ethanol, 10% methanol and 40% acetonitrile, respectively, and the flow velocity was 0.5 m L/min. The recoveries were in the range of 86.95%~106.06% at the spiked level of 5 μg/m L and 10μg/m L. The proposed method allowed the efficient extraction of tyramine in soy sauce in pre-treatment and with high sensitivity, which can be applied to trace analysis of tyramine in food.The optimal functional polymer acrylamide(AM) was screened by computer simulation. Dummy molecularly imprinted polymer on a modified Silica gel matrix was synthesized by surface molecular imprinting method, and succinic acid(SA) was chosed as alternative template, the prepared polymer was called surface molecularly imprinted polymer(SMIP). The results showed that the prepared polymer had high selectivity and adsorption capacity to 3-NPA, in the concentration of 1 mmol/L 3-NPA solution, SA-SMIP showed the best adsorption capacity to 3-NPA which reach to 114.78 μmol/g, the second is(3-NPA)-SMIP, both are much higher than the blank polymer. Specific adsorption experiment results showed that the SA-SMIP had desired adsorption properties to 3-NPA. |
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