Investigation of brush-type chiral stationary phases based on O,O'-diaroyl tartardiamide and O,O'-bis-(arylcarbamoyl) tartardiamide

Four chiral organosilanes based on O,O'-dibenzoyl tartardiamide, O,O'-bis-(3,5-dimethylbenzoyl) tartardiamide, O,O'-bis-(phenylcarbamoyl) tartardiamide and O,O'-bis-[(3,5-dimethylphenyl)carbamoyl] tartardiamide were synthesized and immobilized on silica to afford corresponding brush-type chiral stationary phases (CSPs) with well-defined structures. Using 54 compounds containing a wide variety of structures as analytes, the enantioselectivities of the four CSPs were evaluated under normal-phase modes. 3,5-Dimethyl substituent in the aryl group was found to significantly affect the enantioselectivity of CSPs containing aryl ester moieties. Aryl carbamate moieties in CSPs were observed more beneficial for enantioseparation than aryl ester moieties. The additional hydrogen-bond donors (NH) present in the carbamate groups contributed greatly to the enantioselectivity of CSPs, which is contrary to the results that have been found in network-polymeric CSPs.     

The effect of group IIIA metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6·H2O

A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an 'extra step' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows the highest photocatalytic activity.     

α—氨基酸的快原子轰击质谱

本文研究了１８种α－氨基酸的快原子轰击质谱，发现添加三氟乙酸溶液能显著提高灵敏度，改善谱图。特征碎片主要有中性丢失ＣＯ２Ｈ２，Ｈ２Ｏ，ＮＨ３的离子以及Ｒ＾＋离子。侧链的性质决定了碎片的产生和离子的强弱。     

Bioactivity fingerprint analysis of cyclooxygenase-2 ligands from radix Aconiti by ultrafiltration–UPLC–MSn

A novel fingerprinting method, bioactivity fingerprint analysis, based on an ultrafiltration–ultraperformance liquid chromatography–multistage tandem mass spectrometry (UPLC–MS ⁿ ) method is proposed for the quality control of herbal medicines from the bioactivity viewpoint concerning the efficacy of herbal medicines. The bioactivity fingerprints reflecting the anti-inflammatory activities of radix Aconiti and radix Aconiti preparata were established. With use of ultrafiltration UPLC–MS ⁿ , 11 cyclooxygenase-2 ligands from radix Aconiti preparata and 14 cyclooxygenase-2 ligands from radix Aconiti were found after incubation with cyclooxygenase-2. Twelve of the cyclooxygenase-2 ligands were identified by the ultraperformance UPLC–MS ⁿ method. The enrichment factor of each peak in the bioactivity fingerprint was calculated and was demonstrated to be characteristic, which makes bioactivity fingerprint analysis for the quality control of herbal medicines possible from the viewpoint of their bioactivities.

Fe (III)‐grafted Bi2MoO6 nanoplates for enhanced photocatalytic activities on tetracycline degradation and HMF oxidation

Fe (III)‐grafted Bi₂MoO₆ nanoplates (Fe (III)/BMO) with varying small quantity of Fe (III) clusters modification were fabricated through a simple hydrothermal and impregnation process. The characterization results indicate that the modification of Fe (III) clusters on the surface of Bi₂MoO₆ nanoplates with intimate interfacial contact is beneficial to the expansion of visible light absorption range and the separation of photoinduced carriers during the interface charge transfer process. The photocatalytic properties of the samples were studied by degradation of tetracycline (TC) and selective aerobic oxidation of biomass‐derived chemical 5‐hydroxymethylfuraldehyde (HMF) under visible light. The 1.5 wt% Fe (III) clusters‐grafted Bi₂MoO₆ nanoplates exhibited optimum photocatalytic activity, which is the TC degradation kinetic rate constant is 5.3 times higher than that of bare BMO, and the highest HMF conversion of 32.62% can be obtained with a selectivity of 95.30%. Furthermore, a possible visible light photocatalysis mechanism over Fe (III)/BMO sample has been proposed. This study may supply some insight for the development of visible‐light‐driven Bi₂MoO₆‐based photocatalysts applicable to both environmental remediation and biomass‐derived chemical transformation.     

Combined use of ionic liquid and β‐CD for enantioseparation of 12 pharmaceuticals using CE

In this study, the enantioseparation of zopiclone, repaglinide, chlorphenamine maleate, brompheniramine maleate, dioxopromethazine hydrochloride, promethazine hydrochloride, liarozole, carvedilol, homatropine hydrobromide, homatropine methylbromide, venlafaxine, and sibutramine hydrochloride has been investigated using β‐CD in combination with a chiral ionic liquid (IL), 1‐ethyl‐3‐methylimidazolium‐L‐lactate. The influence of the type of IL and its concentration, BGE pH, and chain length of the IL cations on the resolution are discussed. Finally, the proposed method was successfully applied for the chiral impurity determination of eszopiclone in pharmaceutical tablets after validation with respect to accuracy and precision, linearity range, selectivity, repeatability, LOD and LOQ. It is assessed that the chiral impurity determination in the commercial tables is fewer than 0.1%.     

有机磷化合物的质谱研究(Ⅶ)——二氮二磷杂环戊烷衍生物的化学电离质谱

本文报道了七种4.5-二氧代-2-硫代-1,3,2,4-二氮二磷杂环戊烷衍生物的化学电离质谱(CIMS,甲烷为反应气),结果表明:CIMS中准分子离子MH~+为基峰离子;MH~+离子易发生失去H_2S,CO,C_3H_6等小分子的裂解,(M+C_2H_5)~+离子存在再断裂。     

电感耦合等离子体原子发射光谱法直接测定高纯氧化铈中14个稀土杂质的研究

本文研究了电感耦合等离子体原子发射光谱直接测定99.95%氧化铈中14种稀土杂质的方法。讨论了基体线和光带对分析线的干扰及扣除、并加入70％乙醇提高灵敏度,方法简单,再现性好,准确度高,得到了满意的结果。