紫外光降解水中5-羟甲基糠醛的特性及机理

Characteristics and Mechanism of Photodegradation of 5-Hydroxymethylfurfural in Water Induced by Ultraviolet Irradiation

为研究紫外(Ultraviolet,UV)光降解5-羟甲基糠醛(5-Hydroxymethylfurfural,5-HMF)的特性及机理,该研究构建5-HMF水模拟体系,分析紫外光辐射时间、强度、5-HMF初始质量浓度和光敏剂(FeSO_(4)、TiO_(2)和VB_(2))对5-HMF降解的影响;通过密度泛函理论(Density Functional Theory,DFT)分析5-HMF紫外光降解反应性,并采用超高压液相色谱/四级杆串联飞行时间质谱联用仪鉴定其紫外光降解产物。结果表明:紫外光辐射时间越长,强度越大,5-HMF的初始质量浓度越小,降解率越高;当强度为400μW/cm^(2)、辐射时间为240 min、初始质量浓度为31.5 mg/L时,5-HMF的降解率最大,达83.64%;FeSO_(4)和TiO_(2)对5-HMF的紫外光降解有促进作用,而VB_(2)对其有抑制作用;当FeSO_(4)和TiO_(2)的添加浓度和质量分数分别是1.0 mmol/L和0.025%时,5-HMF的降解率最大,分别为100.00%和76.68%(辐射时间分别为40、80 min,强度400μW/cm^(2));DFT分析结果表明,5-HMF的C=O键更易受到攻击而降解,C4-C11和C1-C8间的化学键易断裂;在UV、UV/FeSO_(4)、UV/TiO_(2)体系中分别鉴定出1、2和5种5-HMF的降解产物;DFT分析结果与质谱鉴定结果相吻合。该研究为降低食品中的5-HMF提供了理论和应用研究基础。

To explore the characteristics and mechanism of ultraviolet(UV)irradiation-induced photodegradation of 5-hydroxymethylfurfural(5-HMF),an aqueous simulation system of 5-HMF was constructed,and the effects of UV irradiation time,light intensity,initial mass concentration of 5-HMF and photosensitizers(FeSO_(4),TiO_(2)and VB_(2))on the degradation of 5-HMF were analyzed.The UV photodegradation reactivity of 5-HMF was analyzed by the density functional theory(DFT),and its UV degradation products were identified by an ultra-high performance liquid chromatography quadrupole time-of-flight tandem mass spectrometer.The results showed that the longer the UV irradiation time,the higher light intensity,the smaller the initial mass concentration of 5-HMF,and the higher the degradation rate.The degradation rate was the highest(83.64%)when the UV irradiation intensity was 400µW/cm^(2),the radiation time was 240 min and the initial mass concentration was 31.5 mg/L.Both FeSO_(4)and TiO_(2)promoted the UV-induced degradation of 5-HMF,whilst VB_(2)inhibited the degradation of 5-HMF.The degradation rates of 5-HMF were the highest when the added concentrations and mass fractions of FeSO_(4)and TiO_(2)were 1.0 mmol/L and 0.025%:100.00%(irradiation time 40 min,light intensity 400µW/cm^(2))and 76.68%(irradiation time 80 min,light intensity 400µW/cm^(2)),respectively.The results of DFT analysis showed that the C=O bond of 5-HMF was more susceptible to attack and degradation,and the chemical bonds between C4-C11 and C1-C8 were easily broken.One,two and five degradation products of 5-HMF were identified in the UV,UV/FeSO_(4)and UV/TiO_(2)systems,respectively.The results of DFT analysis were consistent with the results of mass spectrometry identification.This study provides a theoretical and applied research basis for the reduction of 5-HMF in foods.