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

摘要:

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（FeSO4、TiO2 和VB2）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400 μW/cm2、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%；FeSO4 和TiO2 对5-HMF的紫外光降解有促进作用，而VB2对其有抑制作用；当FeSO4 和TiO2 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400 μW/cm2）；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/FeSO4、UV/TiO2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。

Abstract:

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 (FeSO4, TiO2 and VB2) 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 400 μW/cm2, the radiation time was 240 min and the initial mass concentration was 31.5 mg/L. Both FeSO4 and TiO2 promoted the UV-induced degradation of 5-HMF, whilst VB2 inhibited the degradation of 5-HMF. The degradation rates of 5-HMF were the highest when the added concentrations and mass fractions of FeSO4 and TiO2 were 1.0 mmol/L and 0.025%: 100.00% (irradiation time 40 min, light intensity 400 μW/cm2) and 76.68% (irradiation time 80 min, light intensity 400 μW/cm2), 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/FeSO4 and UV/TiO2 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.