Isolation and purification of flavonoid glycosides from Trollius ledebouri using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase

Three flavonoid glycosides including orientin, vitexin, quercetin-3-O-neohesperidoside and one unknown compound were isolated and purified by high-speed counter-current chromatography (HSCCC) and semi-preparative HPLC from Trollius ledebouri Reichb., a traditional Chinese medicine. Preparative HSCCC with a two-phase solvent system composed of ethyl acetate-n-butanol-water (2:1:3, v/v/v) was successfully performed by increasing the flow-rate of the mobile phase from 1.5 to 2.5 ml/min after 190 min. Consequently, 95.8 mg orientin, 11.6 mg vitexin, 9.3 mg unknown compound with purities of over 97% and one partially purified peak fraction (contained quercetin-3-O-neohesperidoside at 85.1% purity) were obtained from 500 mg of the crude extract. Then the partially purified fraction was further purified by reversed-phase semi-preparative high-performance liquid chromatography. The structure identification of all pure fractions was carried out by UV, MS, 1H NMR and 13C NMR.     

Crystallization and melting behaviors of polystyrene-b-poly(ethylene-co-butene) block copolymers

Non-isothermal and isothermal crystallization behaviors of polystyrene-b-poly(ethylene-co-butene) (PSt-b-PEB) block copolymers with different compositions and chain lengths were investigated by differential scanning calorimetry (DSC). The results show that crystallization of PEB block is strongly dependent on the composition. Crystallization temperature (T_c), melting temperature (T_m) and fusion enthalpy (ΔH_f) increase rapidly with PEB volume fraction (V_E) for block copolymers with V_E below 50%, but there is little change when PEB block becomes the major component. Glass transition temperature (T_g) of the PSt block and order-disorder transition temperature (T_ODT) of block copolymers also have a weak effect. The isothermal crystallization kinetics results show that Avrami exponent (n) was strongly dependent on the composition and crystallization temperature. For the block copolymers with V_E below 38.7 vol%, the values of n vary between 0.9 and 1.3, indicating that crystallization is confined. For the PSt-b-PEB block copolymers with V_E higher than 50%, fractionated crystallization behavior is usually observed. A two-step isothermal crystallization procedure is applied to these block copolymers. It is found that breakout crystallization occurs at higher T_c, but confined at lower T_c. Two overlapped melting peaks are observed for the block copolymers with fractionated crystallization behavior after two-step crystallization, and only the higher melting peak corresponding to breakout crystallization can be used to derive equilibrium melting temperature.     

氨基酸柱前衍生化的3种新荧光试剂的光谱特性及高效液相色谱研究

合成了３种新的荧光标记试剂：吖啶－Ｎ－乙酰氯，咔唑－９－乙酰氯和咔唑－９－丙酰氯。它们的最大发射降激发波长分别为４３０ｎｍ，３６８ｎｍ，和３６５ｎｍ。３种衍生化试剂与氨基酸形成的衍生物在ｐＨ６．５的条件下结合梯度洗脱程序在Ｃ１８反相柱上对色谱条件进行了优化。     

〔Co(H2O)4(NCS)2〕(18-冠-6)的分子和晶体结构

[Co(H_2O)_4(NCS)_2](18-冠-6)的晶体属于正交晶系,空间群:D-P。晶胞参数:a=9.167(2)A,b=13.268(1)A,c=19.292(3)A,Z=4。结构用重原子法解出,经最小二乘法修正,最终的=0.029。钴(Ⅱ)与两个异硫氰酸根、四个水分子配位,形成顺式八面体配位单元,并通过其中的水分子与18-冠-6以氢键相结合,形成标题的分子和晶体。     

Sensitive Voltammetric Response of p‐Nitroaniline on Single‐Wall Carbon Nanotube‐Ionic Liquid Gel Modified Glassy Carbon Electrodes

An ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexafluorophosphate, BMIMPF₆)‐single‐walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF₆‐SWNT/GCE) is fabricated. At it the voltammetric behavior and determination of p‐nitroaniline (PNA) is explored. PNA can exhibit a sensitive cathodic peak at ?0.70 V (vs. SCE) in pH 7.0 phosphate buffer solution on the electrode, resulting from the irreversible reduction of PNA. Under the optimized conditions, the peak current is linear to PNA concentration over the range of 1.0×10^?8–7.0×10^?6 M, and the detection limit is 8.0×10^?9 M. The electrode can be regenerated by successive potential scan in a blank solution for about 5 times and exhibits good reproducibility. Meanwhile, the feasibility to determine other nitroaromatic compounds (NACs) with the modified electrode is also tested. It is found that the NACs studied (i.e., p‐nitroaniline, p‐nitrophenol, o‐nitrophenol, m‐nitrophenol, p‐nitrobenzoic acid, and nitrobenzene) can all cause sensitive cathodic peaks under the conditions, but their peak potentials and peak currents are different to some extent. Their peak currents and concentrations show linear relationships in concentration ranges with about 3 orders of magnitude. The detection limits are 8.0×10^?9 M for p‐nitroaniline, 2.0×10^?9 M for p‐nitrophenol, 5.0×10^?9 M for o‐nitrophenol, 5.0×10^?9 M for m‐nitrophenol, 2.0×10^?8 M for p‐nitrobenzoic acid and 8.0×10^?9 M for nitrobenzene respectively. The BMIMPF₆‐SWNT/GCE is applied to the determination of NACs in lake water.     

8—氮鸟嘌呤的极谱伏安行为

用循环伏安法（ＣＶ）、电流采样极诸法（ＳＣＰ，即ＴＡＳＴ）、常规脉冲极谱法（ＮＰＰ）、微分脉冲极谱法（ＤＰＰ）、线性扫描伏安法（ＬＳＶ）、Ｏｓｔｅｒｙｏｕｎｇ方波伏安法（ＯＳＷＶ）和计时库仑法（ＣＣ）等电化学技术研究了抗癌药物８－氮鸟嘌呤（８－ａｚａｇｕａｎｉｎｅ，ｇｕａｎａｚｏｌｏ，简称８－ＡＧ）的极谱伏安行为．在 ０． １ｍｏｌ／Ｌ Ｈ２ＳＯ４底液中，８－ＡＧ有一良好的还原峰，峰电位（Ｅｐ）在－０． ９５Ｖ（ｖｓ．Ａｇ／ＡｇＣｌ，下同）附近，８－ＡＧ浓度在４×１０－６～８×１０－４ｍｏｌ／Ｌ范围内．峰高与浓度有良好的线性关系，线性相关系数ｒ＝０．９９９９～０．９９１０，检出限为１× １０－６ｍｏｌ／Ｌ．实验证明了该峰具有吸附性．本文提出了电极反应机理，它包括：酸性介质中８－ＡＧ的质子化、质子化的８－ＡＧ在汞电极上吸附以及完全不可逆的两电子还原过程．同时用量子化学计算方法（全略微分重叠法即ＣＮＤＯ／２）对８－ＡＧ和鸟嘌呤的各原子的净电荷以及Ｗｉｂｅｒｇ键级进行了计算，从理论上解释了８－ＡＧ的电化学还原机理。     

Determination of endocrine disruptors in environmental waters using poly(acrylamide-vinylpyridine) monolithic capillary for in-tube solid-phase microextraction coupled to high-performance liquid chromatography with fluorescence detection

A method for the determination of endocrine disruptors, bisphenol A and 17alpha-ethinylestradiol, in environmental water samples was developed using in-tube solid-phase microextraction followed by liquid chromatography and fluorescence detection. A poly(acrylamide-vinylpyridine) monolithic capillary column was applied as the extraction media in view of its greater phase ratio than open-tubular capillaries and thus higher extraction efficiency. After optimizing the extraction conditions, bisphenol A and 17alpha-ethinylestradiol were extracted directly from water samples in a wide dynamic linear range of 0.5-1000 ng mL(-1), with the detection limits obtained as 0.064 and 0.12 ng mL(-1), respectively. The precision of the method was satisfactory with the intraday and interday RSD values smaller than 7.2%. Environmental water samples of different sources were successfully analyzed with the presented method and the monolithic capillary was proved to be robust and reusable in analyzing real water samples.     

Electron Paramagnetic Resonance Study of Radical Pairs and Isolated Radicals Trapped in Irradiated Long-Chain Hydrocarbons at Low Temperatures

The intrinsic characteristics of radical pairs produced in squalane and in cetane receiving high gamma-dose are extensively studied with the EPR technique at temperatures from 77°K up to 150°K. The spectra of the paired radicals occur at g=4 with a very low transition probability in contrast to that of isolated radicals which appear at g=2 A well-resolved hyperfine spectrum corresponding to the species (CH₃CH₂.CH₂CH₃) is observed in cetane. The isothermal decay rates of radical pairs in cetane below 100°K are significantly slow; however, the decay kinetics at 150°K is first order with rate constant=1.86 min^?1. A relatively slower decay rate is obtained for isolated radicals suggesting that the decay mechanism of paired radicals is through geminate recombination. The relative inter-radical distance in radical pairs is known from a decay curve as a function of temperature. The yields of radical pairs are low in both matrices, only few percents of those of isolated radicals. The formation mechanisms of paired radicals with direct radiolytic bond scission process are discussed in connection with the experimental observations.     

New zinc phosphates decorated by imidazole-containing ligands

Four new zinc phosphates [Zn(HPO4)(C6H9N3O2)] (1), [Zn(HPO4)(C4H6N2)].H2O (2), [Zn2(HPO4)2(C14H14N4)].2H2O (3), and [Zn(HPO4)(C14H14N4)] (4) were synthesized in the presence of d-histidine, 1-methylimidazole, 1,4-bis(imidazol-1-ylmethyl)benzene (L1), and 1,2-bis(imidazol-1-ylmethyl)benzene (L2), respectively, and their structures were determined by X-ray crystallography. The inorganic framework of compounds 1, 2, and 3 is composed of vertex-shared ZnO3N and HPO4 tetrahedra that form four rings, which, in turn, are linked to generate a one-dimensional ladder structure. In 1 and 2 the organic groups (monoimidazole ligand) are located at each side of the ladders, while in 3 the bisimidazole ligand, 1,4-bis(imidazol-1-ylmethyl)benzene, links the ladders together to form a novel 2D structure. Compound 1 is the first zinc phosphate framework to be templated by an N-bonded chiral amino acid. In 4 the zero-dimensional four rings are joined together by the linear bridging ligand, 1,2-bis(imidazol-1-ylmethyl)benzene, to generate a one-dimensional framework with a new face-to-face structural motif. The 3D structure of compound 4 is stabilized by hydrogen-bonding, pi-pi interactions, and C-H...pi interactions. The approach of incorporating multifunctional ligands into zinc phosphate frameworks and linking the inorganic zinc phosphates subunits by an organic ligand provides opportunities for the design of new inorganic-organic open frameworks.     

Ultrathin polymer film formation by collision-induced cross-linking of adsorbed organic molecules with hyperthermal protons

A new synthetic approach for the formation of ultrathin polymer films with customizable properties was developed. In this approach, the kinematic nature of proton collisions with simple organic molecules condensed on a substrate is exploited to break C-H bonds preferentially. The subsequent recombination of carbon radicals gives a cross-linked polymer thin film, and the selectivity of C-H cleavage preserves the chemical functionalities of the precursor molecules. The nature and validity of the method are exemplified with theoretical results from ab initio molecular dynamics calculations and experimental evidence from a variety of characterization techniques. Its applicability is demonstrated by the synthesis of ultrathin polymer films with precursor molecules such as dotriacontane, docosanoic acid, poly(acrylic acid) oligomer, and polyisoprene. The approach is fundamentally different from conventional chemical synthesis as it involves an unusual mix of physical and chemical processes including charge exchange, projectile penetration, kinematics, collision-induced dissociation, inelastic energy transfer, chain transfer, and chain cross-linking.