基于“模型认知”的定量实验方案设计的教学实践*——摩尔盐纯度的测定

针对高三定量实验的复习特点,以“摩尔盐纯度的测定”为例进行基于“模型认知”核心素养培养的教学实践。对教学背景、设计思路、教学过程等方面进行研究分析,并从精心选素材,引发模型认知;高质量设问,建构模型认知;点、线、面结合,丰富模型认知等3个角度对促进学生“模型认知”素养提升的化学教学进行分析和阐释。     

Enantioselective high-performance liquid chromatography of aryl-substituted oxazolines as an efficient tool for determination of chiral purity of serine medicinal components

A new approach for the evaluation of chiral purity of serine esterification products bearing long-chain alkyl substituents was developed. The compounds were simply converted to aryl-substituted oxazolines which: (i) facilitates effective chromatographic enantioseparation and (ii) enables direct detection using ultraviolet absorption. The method employs a polysaccharide-based chiral stationary phase and allows enantioseparation of highly stable oxazoline products in less than 6 min using a simple binary mobile phase. As opposed to the previously used normal phase method the developed method was performed in the reversed-phase mode. Aside from the benefits of switching to less hazardous solvents with regard to the principles of Green Chemistry, this has also led to a reduction in the analysis time. In comparison with known serine chromophores, the best enantioseparation of aryloxazoline rigid structure may be achieved only based on non-polar interactions with the chiral stationary phase. In contrast, the substitution of the chromophore moiety with hydroxyl substituent affected intra and intermolecular interactions that caused enantioseparation differences. Concurrently, we found high chirality retention of (R)- and (S)-configuration oxazoline standards (≥99% enantiomeric excess) during the introduction of the ultraviolet label. The method is suitable for rapid injection of the mixture containing the ultraviolet absorption marker without prior purification.     

色谱柱分类数据库用于指导天然药物化学对照品色谱纯度测定时色谱柱理性选择

由于中药化学对照品多数来源于动植物药材,很容易混有结构类似物,故有机杂质测定是可能影响其化学对照品赋值准确性的关键风险因素。中药化学对照品的有机杂质测定通常采用药典收载或文献报道的高效液相色谱法,这些方法通常仅规定“以十八烷基硅烷键合硅胶为填充剂”,无适宜色谱柱的品牌信息,或者实验室无文献所用的色谱柱品牌,而目前市场上已有800多种品牌的C₁₈柱,生产工艺的不同导致不同品牌C₁₈柱的选择性有差异,甚至差异显著。这很容易出现由于色谱柱选择不适宜而导致测定结果不准确的风险。该文采用国外色谱柱分类数据库指导对照品纯度考察时色谱柱的理性选择,尽可能减少色谱柱盲选可能导致的纯度结果不准确的风险。首先,用数据库挑选2根选择性差异显著的色谱柱（选择性因子F≥6）进行平行实验,以尽可能反映采用不同品牌色谱柱可能出现的分离效果差异。如果这2根色谱柱的分离效果及纯度测定结果无显著性差异,则可以交叉验证该对照品纯度测定的准确性。否则需要从数据库中选择另外1根与之前试验中分离效果更好、选择性相似的色谱柱进行纯度结果验证。在N-反式-p-对香豆酰基酪胺和表儿茶素没食子酸酯首批对照品的纯度考察中,使用了上述策略并验证了其有效性和科学性,计划推广应用至更多的中药化学对照品,特别当其可能含碱性或弱酸性化合物时,更应该尝试采用本文推荐的色谱柱选择策略交叉验证其纯度测定结果的准确性。     

An improved and practical route for the synthesis of enzalutamide and potential impurities study

An improved and practical synthesis of enzalutamide was accomplished in five steps. Starting from 4-bromo-2-fluoro-benzonic acid, a methyl esterification, Ullmann ligation, methyl esterification, ring closing reaction and final methyl amidation provided the target in 35% total yield with 99.8% purity. Five identified impurities were also synthesized. This efficient and economical procedure avoids the use of highly toxic reagents and multiple recrystallization operations, which is suitable for further industrialization.     

A comparison of quantitative nuclear magnetic resonance methods: internal,external, and electronic referencing

The performance of three quantitative NMR methods was compared in terms of short‐term and long‐term precision and accuracy, robustness, linear range, and general applicability. The Internal Reference method employs a reference material co‐dissolved with sample; the External Reference method employs a reference material contained in a separate solution; and the third method, known as Electronic REference To access In vivo Concentrations (ERETIC), employs an externally calibrated digital reference peak. The Internal Reference method results were the most precise and remained stable within 0.1% for at least 4 weeks. The results from the External Reference and ERETIC methods were practically equivalent to each other during this time. These methods exhibited small differences relative to the standard set by the Internal Reference method and slightly lower precision, establishing them as practical alternatives to the Internal Reference method. In contrast to the Internal Reference method, the External Reference and ERETIC methods possess several advantages that address peak overlap, flexibility of calibration, and duration of applicability. The study was designed such that each spectrum contained the information needed to compare the three methods while all other variables were kept constant. Applicability of pulse width compensation is addressed. ERETIC software compensation and minor adjustments to 90° pulse width were concluded to be unnecessary for this system. Although each of the methods was applied here to specifically calculate and compare chemical purity values, this evaluation applies generally to absolute quantitation by NMR. Copyright © 2013 John Wiley & Sons, Ltd.     

Efficient production of nanoporous silicon carbide from rice husk at relatively low temperature

Nanoporous silicon carbide with a specific surface area of up to 186.45 m² g⁻¹ has been efficiently synthesized from waste rice husk using a magnesiothermic reduction at 950 °C as a key step. Throughout the entire process, the recovery rates of silicon, potassium and phosphorus from rice husk can reach 88.46, 91.5 and 65.5%, respectively. Turning rice husk waste into a real treasure, this promising method for producing porous SiC protects the environment and brings economic benefits.     

Nanoparticles as macromolecules

A review of recent trends in the dispersion, purification, and assembly of colloidal nanoparticles highlights a number of growing analogies with ideas borrowed from polymer science. Beyond the similar scales of size, several key concepts lying at the foundation of polymer physics—such as polydispersity, fractionation, phase ordering, and viscoelasticity—are taking on new and unique significance in the contemporary realm of nanotechnology. Leveraging “soft matter” at the nanoscale to simplify materials processing and improve material performance is becoming a reality, with potentially profound implications for a number of emerging technologies. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013 , 51, 1195–1208     

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%.     

Quantitative NMR (qNMR) for pharmaceutical analysis: The pioneering work of George Hanna at the US FDA

In the last two decades, quantitative NMR (qNMR) has become increasingly important for the analysis of pharmaceuticals, chemicals, and natural products including dietary supplements. For the purpose of quality control and chemical standardization of a large variety of pharmaceutical, chemical, and medicinal products, qNMR has proven to be a valuable orthogonal quantification method and a compelling alternative to chromatographic techniques. This work reviews a fundamental component of the early development of qNMR, reflected in the pioneering work of the late George M. Hanna during the years between 1984 and 2006 at the US Food and Drug Administration (FDA). Because Hanna performed the majority of his groundbreaking work on a 90‐MHz instrument, his legacy output connects with recent progress in low‐field benchtop NMR instrumentation. Hanna gradually established the utility of qNMR for the routine quality control analyses practiced in pharmaceutical and related operations well ahead of his peers. His work has the potential to inspire new developments in qNMR applied to small molecules of biomedical importance.     

NMR 77Se, 125Te, 31P and Structure of Seleno-and Telluro-Phosphorus Compounds

Spectra of a nuclear magnetic resonance of seleno- and telluro-phosphorus compounds on nuclei ⁷⁷Se, ¹²⁵Te, ³¹P are described. The dependences of spectral parameters on a structure of the substitutes at phosphorus atom in these compounds are discussed.