| By taking Sudan red I as templates, modifying rosin as cross-linking agent and using acrylic amide as functional monomer, this thesis adopts the method of suspension polymerization to synthesize Sudan red I molecularly imprinted polymer and then it selects the optimum synthetic condition. Meanwhile, some further research is down on the adsorption performance of synthetic polymer, the separatability of MIP imprinting, and recognition performance of the molecular, through which a new method to rapidly examine the prohibited pigment-- Sudan red I in food has been found by establishing a molecularly imprinted solid phase extraction and high performance liquid chromatography(SPE-HPLC). Specific research procedures are as follows:1.Synthetic conditions of molecular imprinting were optimized through single-factor experiment, and the repetitive experiments results showed that the synthetic conditions possess high stability and excellent repetitiveness. In the same conditions, compared with commonly used cross-linking agent(EGDMA> MBA TRIM), the experiments results indicated that among the four kinds of polymer,the synthetic MIP with modified rosin as cross-linking agent owns highest cross-linking degree, good mechanical strength, excellent resistance to high temperature and high pressure2. The physical and chemical performances of polymer were tested, and the results showed that the cross-linking degree of synthetic molecularly imprinted polymer is 98.31%, the average mechanical strength 605.16g, and Softening point 310℃. Meanwhile, synthetic molecularly imprinted polymer can’t be dissolved in the commonly used organic solvents such as Octane, petroleum ether and gasoline, cyclohexane, ethyl acetate, ethanol, acetonitrile etc. It is resistant to strong acid but not to alkalis, and can slightly be dissolved in di-methyl sulf-oxide and N, N-dimethyl formamide. As it is shown in the SEM chart, MIP possesses micro-spherical appearance, and the particle size is uniform in distribution, and between 165～180 μ m, particles are smaller, which is quite suitable for solid phase extraction packing. In addition, it owns fine linear dimension and hollow structure.3.The method of thermogravimetric analysis, infrared absorption spectrum and ultraviolet absorption spectroscopy, X-ray powder diffraction, elemental analysis and scanning electron microscopy(sem) etc, respectively, were used to characterize the structure of MIP. The results indicated that Sudan red I, acrylamide and crosslinking agent react at a certain proportion. The surface structure of molecularly imprinted polymer could be observed from the result of scanning electron microscopy (sem). The surface is full of cavities which is in favor of the absorption of Sudan red I, while NIP is smooth, and its surface has less cavities which provides another strong evidence that the MIP has a good adsorption for Sudan red I.4. Ethyl acetate is the best solution for Sudan red I to be absorbed by MIP. With oscillation frequency for 80rpm and absorption for 5h,at the condition of 30℃, the results showed that the adsorption rates gradually reduced with the increase of experimental time, and its adsorption balance time was about 5h, and the entire adsorption process could be considered as slow adsorption process.5. The equation of Langmuir, Freundlich and Scatchard, respectively, was used to fit the adsorption isotherms, with Langmuir equation correlation coefficient for R2= 0.8951, Freundlich equation correlation coefficient for R2=0.9254, fitting correlation coefficient for R2= 0.9983 and R2= 0.9552 fitting to Scatchard equation. Calculating through Langmuir equation, the maximum adsorption of MIP is Qmax=21.32mg/g while calculating through the Freundlich equation, the maximum adsorption of MIP is Qmax=:13.37mg/g. Both the maximum adsorptions were less than the experimental value, which demonstrated that the flaws existed in this experiment by using these two equation to test the adsorption thermodynamics of MIP. Thus, it is not a really reflection of adsorption behavior of MIP. Two straight lines of the linear regression equation O/Ce=-3.7126 Q+44.671 (R2=0.9983); O/Cc 0.2372Q+20.623 (R2=0.9552) were obtained by using Scatchard model to fit two better lineation parts. The binding site of MIP was obtained by figuring out the slope and the intercept of two linear equation:high-affinity binding site for =0.2694 (mg/ml), Qmax1=12.03, Low-affinity binding site for=4.216 (mg/ml), Qmax2=86.95mg/g. It Used Scatchard equation to describe that Sudan red I adsorption behavior of MIP is better than that of Langmuir equation and Freundlich equation。6. The specific adsorption of MIP was probed by the static adsorption experiments between Molecularly imprinted polymer (MIP), none molecularly imprinted polymer (NIP) and the template molecular, the structural similar compound. The separation selectivity of MIP was studied by the competitive adsorption experiment of MIP in the template and structural similar hybrid system to the template molecular. The experimental results showed that, the imprinting factor a of MIP to Sudan red I is 2.09, significantly more than the imprinting factor to that of Sudan red Ⅱ, Ⅲ, Ⅳ; Competitive adsorption experimental results showed that, adsorption amount of MIP to Sudan is greater than Sudan red Ⅱ, Ⅲ, Ⅳ, and the separation factor β, respectively, was 2.23、4.04 and 14.32. Therefore, Sudan red I adsorbed by MIP was considered as "preferential adsorption," and it could be easily absorbed by MIP, which turned out that MIP possesses high specific adsorption and good separation selectivity to Sudan red Ⅰ. On the contrary, NIP doesn’t possess this kind of molecular recognition and selectivity.7. In this paper, the same mass solid phase extraction column (MISPE) were made by MIP and C18 packing, two components of mixed system, respectively, made by Sudan red Ⅰ and Sudan red Ⅱ, Ⅲ, Ⅳ. The contrastive absorption experiments of dynamic analyses were made through MISPE and C18 column. As could be seen from the data, the imprinting factor a of Sudan red Ⅰ, with MISPE were 2.19,1.76 and 1.80 respectively, all over 1.5, which demonstrated that Sudan red I is specifically adsorbed by MISPE. Judging by the separation factor data, the separation factors of MISPE were 1.26、1.89 and 1.74 respectively, over 1, while the separation factors of C18 column,were 0.87,1.13 and 1.04 respectively. The experimental results explained that MISPE has predominant recognition and selection separating property. However, the adsorption amount of C18 column to Sudan red Ⅰ, and Sudan red Ⅱ, Ⅲ, Ⅳ is not significantly different. Thus, C18 does not have this kind of molecular recognition and selectivity.8.In this paper, a novel method based on molecularly imprinted solid phase extraction followed by high performance liquid chromatography (HPLC) has been developed for the analysis of prohibited pigment Sudan red Ⅰ in food. Meanwhile, it used synthetic Sudan red Ⅰ MIP as solid phase extraction packing to synthesize molecularly imprinted solid phase extraction column (MISPE) and then the solid phase extraction conditions were optimized by reversing phase high performance liquid chromatography. After adding the standard spike in the recovery experiment, the recovery rate turns out to be between 84.40% 95.59%, and RSD 0.44%-1.27%, which indicted the high precision and better accurate of this method.What’s more,22 kinds of merchant food sample (such as bagged black tea, Ham and egg, chili oil etc) were detected by the method of HPLC combined with solid phase extraction technology. Although the positive samples that contain Sudan red I, haven’t been found, the established method in this experiment provides a new approach and an effective basis for rapidly screening the Sudan I in food. |
PDF Full Text Request