HPTLC fingerprint identification of commercial ginseng drugs - reinvestigation of HPTLC of ginsenosides

The optimized HPTLC of ginsenosides reported in this paper shows that the recommended solvent system has a higher resolution, greater spot capacity, and better reproducibility by comparison with the established ones in the previous literature. Detection and scanning in the fluorescence mode after visualization with 5% sulfuric acid/EtOH by the dipping technique improved and enhanced the sensitivity by a factor of nine compared to the commonly used absorbance made. Sample pretreatment by an adsorption clean-up step on a small alumina column followed by 1-butanol extraction instead of only a butanol-extraction step made the chromatogram clearer, caused less background contamination, and reduced the tailing of some ginsenosides spots. The ‘peak grouping’ method was effectively used in HPTLC fingerprint identification of various commercial ginseng medicines and the chromatograms of roots of ginseng (white and red; Panax ginseng), American ginseng (P. quinquifolium), and sanchi (P. notoginseng) obtained under recommended condition are perfectly recognizable.     

Reversed-phase thin-layer chromatography of various pesticides in the presence of water-soluble beta-cyclodextrin polymer

Summary The modification of the hydrophobicity of 28 commercial pesticides with a water-soluble -cyclodextrin polymer (SCDP) in the presence of aqueous NaCl has been studied by reversed-phase thin-layer chromatography. The pesticides formed inclusion complexes with SCDP and these complexes are less lipophilic than the parent pesticides. The sodium chloride exerted a typical saltingout effect, the retention of each pesticide increased with increasing concentration of the salt in the eluent. This effect can be tentatively explained by the suppression of the dissociation of the polar groups in the solute molecules resulting in increased apparent lipophilicity. The correlation between lipophilicity and salting-out effect was found to be significant, that is the salting-out effect increases with increasing polarity (lower lipophilicity) of the pesticides, whereas the lipophilicity has negligible influence on the inclusion-forming capacity of non-homologous series of pesticides.     

Vaporising systems for large volume injection or on-line transfer into gas chromatography: Classification, critical remarks and suggestions

Techniques for large volume introduction of liquid samples into capillary gas chromatography (GC) follow a small number of principals. Vaporising systems, vapour discharge modes and methods for solvent-solute separation are classified and evaluated.

Presently, programmed temperature vaporising (PTV) solvent split injection is the preferred method if on-column techniques cannot be applied. Critical re-evaluation suggests, however, that solvent evaporation and solvent-solute separation should be performed in separate compartments and optimized individually. Permanently hot chambers offer the highest capacity for solvent evaporation. The preferred techniques for solvent-solute separation are stationary phase focusing in a coated capillary or solvent trapping in an uncoated capillary precolumn. The vaporising chamber-precolumn solvent split-gas discharge system is proposed for large volume injection and on-line transfer of water-containing solvent mixtures, and in-line vaporiser-precolumn solvent split-overflow system for most on-line transfer applications.     

On capital injections and dividends with tax in a classical risk model

Consider the classical risk model with dividends and capital injections. In addition to the model considered by Kulenko and Schmidli (2008), tax has to be paid for dividends. Capital injections yield tax exemptions. We calculate the value function and derive the optimal dividend strategy.     

Hyaluronic Acid Nanoporous Microparticles with Long In Vivo Joint Residence Time and Sustained Release

A simple approach is reported to engineer biodegradable and biocompatible nanoporous hyaluronic acid particles (NPHAs) with a characteristic sponge‐like morphology and uniform size. These NPHAs can be synthesized using the concomitant cross‐linking of hyaluronic acid and the cross‐linking agent precipitation. The nanoporous architecture of NPHAs prevents the rapid enzymatic degradation of hyaluronic acid and controls the erosion of microparticles in physiological conditions. Once injected into an intra‐articular body cavity of healthy mice, these NPHAs reside at the point‐of‐delivery for an extended time period, exhibiting a sustained release of hyaluronic acid. In addition, in vivo studies indicate the persistence of NPHAs in the knee joints with neither accumulation into major organs, nor any local or systemic side‐effect. The use of NPHAs is emphasized as reservoirs of hyaluronic acid, effectively providing an innovative and safe platform for prolonging the favorable effects displayed by hyaluronic acid on joints affected by osteoarthritis.     

多次喷射对重型柴油机影响的试验研究

本文在一台电控共轨柴油机上进行了多次喷射及多次喷射和EGR结合对重型柴油机影响的试验研究。EGR为基于VGT的高压冷却EGR系统。研究了不同喷射策略下喷射参数对柴油机性能和排放的影响。研究了EGR和多次喷射结合降低柴油机排放的效果;通过调整EGR率,将NO_x控制在2.0 g/(kW·h),研究喷射参数和EGR对柴油机的影响。研究结果表明,预喷射可以在小负荷时改善柴油机的NO_x、CO和比油耗,但在大负荷时没有明显的影响;两次预喷射可以促进油气混合;后喷射可以促进油气混合,提高碳烟的氧化速度,因而可以明显改善柴油机的烟度和CO;优化的喷射参数结合EGR可以显著降低NO_x和烟度。     

Industrial scale production of Selectfluor™ fluorination agent: from initial concept to full scale commercial production in a 5 year period

The Selectfluor™ electrophilic fluorination agent 1 is now produced in multi-ton per year quantities and is one of only a few fluorine-containing fine chemicals that are produced by direct fluorination with F₂ on an industrial scale. From the initial concept of the “ideal fluorination agent” to the present day industrial scale production of Selectfluor™, the route to the successful commercialization included a series of critical steps. A chronological account of the road to commercialization of Selectfluor™, noting the important product development factors, is provided herein.     

论商业银行资产负债比例管理控制论系统

本文提出了商业银行管理创新的观点,作者将金融理论、控制论、系统论有机地结合起来,提出并论证了一种新的银行管理方法商业银行资产负债比例管理控制论系统.     

民国时期“复兴”初高中化学教科书述评

"复兴"化学教科书由商务印书馆在20世纪30年代初出版,内容丰富,体系完整,注重联系国情。其使用贯穿整个三四十年代,是民国时期的代表性化学教科书。但也存在初、高中教材内容重复,化学理论未充分发挥指导作用,教科书栏目和实验设置不足等局限。