Microwave Preparation Of Modified Chitosan And Determination Of Amaranth In Beverage

In recent years,the abusive problem of edible synthetic pigment has attracted people's attention.Through the body metabolism,edible synthetic pigment is much likely to form carcinogenic substances,producing a certain harm to the human body.HPLC,HPCE,ELISA,etc.are the common methods for edible synthetic pigment.Although the sensitivity is high,the cost is relatively high.Modified chitosan can separate and enrich effectively for edible synthetic pigment in beverage,and using UV-Vis spectrophotometry to detect it.This method is easy to operate,low cost,good separation effect,and it is widely used in the separation,enrichment and detection for synthetic pigments in beverage.In this paper,the novel modified chitosan was microwave synthesized by the chitosan and organic ligand via two synthetic routes,and the optimum synthesis conditions was discussed.The adsorption properties of modified chitosan to amaranth were studied.The modified chitosan with excellent performance was screened out,which was combined with UV-Vis spectrophotometry and then applied to the separate,enrich and detect for amaranth in beverages.The main contents are as follows:(1)By single factor experiment,the optimum reaction temperature,reaction time,reaction molar ratio of microwave synthesis for 2,6-diaminopyridine modified chitosan(DACTS),3-amino-1,2,4-triazole modified chitosan(TCTS),2-amino-3-hydroxypyridine modified chitosan(ACTS),thiourea modified chitosan(TCCTS)had been verified.Element analysis was used to determine nitrogen content of modified chitosan to calculate the percentage of functional group conversion,and the percentage of functional group conversion of DACTS,TCTS,ACTS and TCCTS were 41.48%,36.24%,35.67%and 33.66%,respectively,and two kinds of modified chitosan were screened out.The structures of the two modified chitosans were characterized by FTIR and TGA.The possible synthetic methods,pathways and possible structures of the modified chitosan were deduced and the thermal stability was also discussed.(2)The adsorption properties of two modified chitosan for amaranth were studied.The results showed that DACTS and TCCTS both had higher adsorption capacities for amaranth,and the saturated adsorption capacity were 488.7 mg/g,533.3 mg/g,respectively,and the optimal adsorption pH were 3.The kinetic adsorption kinetics of DACTS and TCCTS all accorded with the second-order kinetics model,suggesting that is chemical adsorption.The isotherm adsorption of DACTS and TCCTS followed Langmuir model,which suggested that both of them were monolayer preferential adsorption.Thermodynamic functions indicated that the adsorption process of DACTS and TCCTS for amaranth were endothermic and spontaneous adsorption.The results of static desorption and regeneration experiments show that the best desorption agent of DACTS and TCCTS was 2 mol/L NaOH solution,the maximum desorption rate was 96.6%and 95.4%respectively.Repeated experiments showed that DACTS and TCCTS had good regenerative capacity and reusability after 5 times in adsorption-desorption experiments.The dynamic adsorption process of DACTS to amaranth was consistent with Thomas model,and the saturated adsorption capacity was 632.6 mg/g.The Zeta potentials of modified chitosan were analyzed by electrophoretic light scattering.The results showed that modified chitosan was favorable for the adsorption of amaranth on acidic condition.SEM analysis was used for characterizing DACTS and TCCTS.The results showed that the modified chitosan had a large amount of granular materials.(3)A method based on modified chitosan and ultraviolet-visible spectrophotometry was developed for the enrichment and determination of amaranth in beverages.The method has the advantages of low cost,good separation effect,high precision and anti-interference ability.In this paper,the optimum preconcentration conditions of DACTS were discussed and applied to the determination of amaranth in carbonated beverage and prepared wine.The results showed that the data of the two methods were almost consistent.The method can be applied to analyze and detect amaranth in beverages,and the detection cost is cut down.