Preparation Of 4-vinylpyridine Material And Evaluation Of Its Adsorption Performance For Synthetic Pigments

The appearance,color,smell,taste and hardness of food are the five major elements of sensory identification of food quality,among which color will directly affect people's perception of food and appetite.However,most of the food cannot maintain its original colour after being processed into food or the original colour is not enough to stimulate people's appetite,so businesses use food colorants to give and improve the colour of food.Synthetic pigments have no nutritional value and excessive intake will do harm to the body.Therefore,various countries have strict regulations on the scope and limit of use of synthetic pigments and have established corresponding detection methods.Sample pretreatment is very important to the accuracy of the pigment detection.With the development of food industry,there are more and more kinds of food and more and more complex food matrices.The existing pretreatment material cannot completely meet the needs of the detection,therefore developing and using low cost,simple operation and more environmentally-friendly new pretreatment materials of artificial synthetic pigments is of great significance to the development of detection technology.In this paper,a solution precipitation controllable polymerization method was used to synthesize an activity of poly(styrene-co-ethylene glycol dimethacrylate)(poly(St-co-EGDMA))for nuclear,4-vinylpyridine(4-VP)as the functional adsorption layer is synthesized by solution precipitation controlled polymerization to develop an adsorbent for artificial pigment in food sample pretreatment.The main contents of this paper are as follows:(1)In combination with molecular imprinting technology,a nucleus-shell molecularly imprinted polymer MIP(MIP-PS-4VP)with selective adsorption of tartrazine was attempted to be prepared on the surface of poly(St-co-EGDMA)nucleus with chain transfer groups,using tartrazine as the imprinting template,4-VP as the functional monomer,and EGDMA as the cross-linking monomer.The adsorption capacity and selectivity of molecularly imprinted polymers to pigments were evaluated by isothermal adsorption and actual sample adsorption experiments.Isothermal adsorption experiments showed that MIP had a slight advantage over non-molecularly imprinted polymer NIP(NIP-PS-4VP)(no template molecules were added during preparation)in pure solution.In the actual sample experiment,the imprinting effect and adsorption selectivity of molecularly imprinted polymesr are not obvious,and can absorb a variety of food pigments.This is because MIP has a strong adsorption capacity for pigments,which masks the imprinting hole effect of the imprinting material.The experimental results also show that the absorption capacity of poly(styrene-co-4-vinyl pyridine)core-shell polymer(PS-4VP)for pigment is better than that of polyamide used in the national standard method,and it is a potential pigment adsorption material to replace polyamide.(2)Poly(St-co-EGDMA)nuclei with chain transfer groups on the surface were synthesized by solution precipitation controlled polymerization,and then poly(St-co-EGDMA)@poly(4VP-co-EGDMA)composite polymers(PS-4VP)were synthesized by precipitation polymerization on poly(St-co-EGDMA)nuclei.The adsorption capacity of the material on five representative synthetic food colorants under different pH conditions was studied,and the maximum adsorption capacity for various pigments under the optimal adsorption pH conditions was compared with that of polyamide adsorbent.The experimental results show that the material has good adsorption capacity for five kinds of pigments,and the recovery rate of addition in the actual sample is better than the polyamide used in the national standard method.The results of repeated use experiments showed that the material could be reused for more than 10 times,the recovery rate remains stable,and the amount of material used in the experiment is small(5?20 mg),the amount of sample is small(1 m L),the pretreatment time is short(5?10 min),less solvent consumption and environmentally friendly use.protection.(3)Prepare packing materials suitable for solid phase extraction.Using divinylbenzene(DVB)as a crosslinking agent to synthesize poly(St-co-DVB)cores,explore the method of preparing micron-level polystyrene cores.The experimental results show that EGDMA in DVB alternative work(2)is used as a cross-linking agent to prepare large-diameter polystyrene nuclei with better nucleation shape,which avoids agglomeration and provides the possibility of uniform coating of subsequent functional adsorption layer.