人参果浆中人参皂苷Re的提取和生物转化

为了充分利用人参资源,本文以加工厂废弃的人参果浆为原料,分析人参果浆中的皂苷含量和组成,并从中提取人参皂苷Re,以人参皂苷Re为底物,采用人参自身酶为催化剂,生物转化得到人参皂苷Rg2组。结果表明,人参加工厂废弃果浆的干品中,皂苷含量为6.21%(W/W),其中人参皂苷Re的含量为55.1%(W/W)。从果浆的干品中提取纯化得到了人参皂苷Re,得率为2.4%(W/W)。人参皂苷Re生物转化制备得到人参皂苷Rg2组,得率为65%(W/W)。经高效液相色谱(HPLC)及超高效液相-四级杆飞行时间串联质谱(UPLC-Q-TOF-MS)分析得出,人参皂苷Rg2组由20(S)-Rg2、20(R)-Rg2、Rg4和Rg6组成,本论文为人参加工厂废弃果浆的综合利用提供了理论依据。     

质谱能量分辨曲线法快速区分香豆素类位置异构体

利用超高效液相色谱-四极杆-飞行时间质谱(UHPLC-Q-TOF MS)技术,结合能量分辨曲线,建立了快速区分香豆素类位置异构体的方法。对互为位置异构体的化合物施加2～40 V的动态碰撞能量,以位置异构体中分子质量相同且丰度百分比差异较大的1对碎片离子绘制能量分辨曲线。实现了单取代线型、双取代线型和角型呋喃香豆素以及简单香豆素各类位置异构体的快速区分。依据质谱的高分辨及高灵敏的特征,根据碎片离子的丰度差异,推测了双取代线型呋喃、角型呋喃及简单香豆素产生丰度差异的碎裂机理。结果表明:4对5,8单取代线型呋喃香豆素类、1对双取代线型呋喃香豆素、1对双取代线型和角型呋喃香豆素和1对简单香豆素的能量分辨曲线表现出明显差异。本实验通过质谱能量曲线法对上述7对香豆素类位置异构体进行区分,其中5,8位双取代线型呋喃香豆素、角型和线型呋喃香豆素、双取代简单香豆素这3对位置异构体,首次通过能量分辨曲线发现了丰度有明显差异的1对碎片离子。该方法操作简单,质谱能量分辨曲线差异明显,能够实现在无对照品的情况下快速区分这7对香豆素类位置异构体。     

烟碱手性异构体的分离分析

建立了烟碱手性异构体的高效液相色谱分离分析方法。采用CHIRALPAK IG-3手性色谱柱,流动相:30%乙腈-70%20 mmol/L碳酸氢铵水溶液,可有效分离烟碱手性异构体。以天然左旋烟碱为标准品,采用外标法在260nm波长检测,结果表明:在0.0001～0.01 g/mL范围内,左旋异构体的峰面积与其质量浓度呈现良好的线性关系,决定系数(R2)为0.999,方法的检出限为9.3×10^-8g/mL,平均回收率99.4%,相对标准偏差小于0.5%(n=8),准确度和重现性较好。烟碱手性异构体的响应因子为1.01,可以采用归一化法测定左右旋异构体相对含量。     

Dithieno[3,2-f:2′,3′-h]quinoxaline-Based Photovoltaic–Thermoelectric Dual-Functional Energy-Harvesting Wide-Bandgap Polymer and its Backbone Isomer

Both organic solar cells (OSCs) and organic thermoelectrics (OTEs) are promising energy-harvesting technologies for future renewable and sustainable energy sources. Among various material systems, organic conjugated polymers are an emerging material class for the active layers of both OSCs and OTEs. However, organic conjugated polymers showing both OSC and OTE properties are rarely reported because of the different requirements toward the OSCs and OTEs. In this study, the first simultaneous investigation of the OSC and OTE properties of a wide-bandgap polymer PBQx-TF and its backbone isomer iso-PBQx-TF are reported. All wide-bandgap polymers form face-on orientations in a thin-film state, but PBQx-TF has more of a crystalline character than iso-PBQx-TF, originating from the backbone isomeric structures of α,α ′/β,β ′-connection between two thiophene rings. Additionally, iso-PBQx-TF shows inactive OSC and poor OTE properties, probably because of the absorption mismatch and unfavorable molecular orientations. At the same time, PBQx-TF exhibits both decent OSC and OTE performances, indicating that it satisfies the requirements for both OSCs and OTEs. This study presents the OSC and OTE dual-functional energy-harvesting wide-bandgap polymer and the future research directions for hybrid energy-harvesting materials.     

Rapid identification of volatile organic compounds and their isomers in the atmosphere

Isomers are widely present in volatile organic compounds (VOCs), and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere. In this work, laser-induced breakdown spectroscopy (LIBS) technology was developed to online distinguish VOCs and their isomers in the air. First, LIBS was used to directly detect halogenated hydrocarbons (a typical class of VOCs) and the characteristic peaks of the related halogens were observed in the LIBS spectra. Then, comparing the LIBS spectra of various samples, it was found that for VOCs with different molecular formulas, although the spectra are completely the same in elemental composition, there are still significant differences in the relative intensity of the spectral lines and other information. Finally, in light of the shortcomings of traditional LIBS technology in identifying isomers, machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs, and the recognition results were very good. It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.     

Influence of n-butanol and isomers on the combustion mechanisms of isooctane and coke formation based on ReaxFF simulation

Fuel additives play a significant role in enhancing the thermal stability of fuel combustion. The effect of additives on the combustion of hydrocarbon fuels and the combustion performances of isooctane with three different isomer additives, (n-butanol (1-BuOH), diethyl ether (DEE), and 2-butanol(2-BuOH)), and additive-free isooctane were explored by ReaxFF simulation in this work. The simulation system was heated to 3000 K at a heating rate of 10 K/ps and kept stable at 3000 K. A variety of combustion products (e.g., small gas molecules and C1-C8 hydrocarbon compounds) in each system were analyzed, and the reaction paths were speculated based on the computed trajectory. The simulation results showed that the C C bond scission reaction dominated the combustion process of the three additives. All three additives promote the formation of toxic carbonyl compounds such as formaldehyde, while the pure DEE additive has the best inhibition effect on the formation of the coke precursor, C₂H₂, C₃H₄, and C₃H₆. The pure 1-BuOH additive can shorten the initial reaction time of the reactants. The effects of DEE/1-BuOH additive on the combustion of isooctane were investigated to obtain a desirable additive mixture with good performance. The expansion of the DEE proportion (80%/20% DEF/1-BuOH) shows a slightly better coke (C₃H₄ and C₃H₆) reduction effect, while the inhibition effect is not as obvious as that of a pure DEE additive.