系统指纹定量法鉴别龙胆泻肝丸质量

建立龙胆泻肝丸(Longdanxiegan pill,LDXGP)的高效液相色谱(HPLC)指纹图谱,以系统指纹定量法评价其质量.采用RP-HPLC法,以宏定性相似度为参量对12批LDXGP进行聚类分析,确定用其中10批生成对照指纹图谱(RFP),以此RFP为标准用系统指纹定量法评价12批LDXGP质量.以龙胆苦苷为参照物峰,确定60个共有指纹峰,建立了LDXGP的HPLC指纹图谱.用系统指纹定量法鉴别出8批质量合格,1批含量明显偏高,1批含量明显偏低,2批化学成分数量和分布比例不合格.系统指纹定量法将整体定性分析和整体定量分析密切结合,是评价中药质量的有效方法.     

化学指纹图谱的相似性测度及其评价方法

提出化学指纹图谱相似性测度概念,并以峰数弹性、峰比例同态性和峰面积同 态性为评价指标,用于多角度评价化学指纹图谱相似性测试优劣,根据这些评价指 标,用计算机仿真方法研究比较了6种相似性测度,结果表明夹角余弦测试用于度 量指纹图谱间谱峰比例的波动较适宜,峰匹配测度可较灵敏地检测小峰个数波动, 而欧氏距离测试则具有较好的综合评价能力。最后,采用实测的参麦注射液色谱分 析谱图。研究考察了上述计算机仿真实验结果,证明仿真结果符合实际情况,这表 明本研究方法可用于评价化学指纹图谱相似性测度。     

红外光谱分析数据特征指纹的可视化表达方法

提出一类红外光谱分析数据特征指纹的可视化表达方法。该方法采用基于贝叶斯准则的多元统计方法对原始数据进行投影变换，再以地维灰度图对变换后数据进行可视化表征，形成基于计算机图像的虚拟化学指纹图谱。将其用于鉴别3种不同产地中药当归样品的结果表明，它能有效提取红外光谱分析数据的特征指纹，实现以虚拟指纹图谱对药材产地的分类鉴别，从而为辨识复杂化学物质体系提供了新的技术手段。     

Testing the polarity and adsorptivity of nondeactivated GC capillary surfaces

Split injection of 1-pentanol headspace on to raw or treated fused silica tubing yields information on the characteristics of its surface (silanol concentration, polarity, adsorptivity). Fused silica tubing from three sources was compared. The effect of various leaching and etching procedures used for column preparation was studied, as was the stability of uncoated fused silica precolumns towards water and some organic solvents.     

用热解吸处理样品-气相色谱与质谱联用法建立烟用香精指纹图谱及其在烟用香精质量控制中的应用

采用热解吸-气相色谱-质谱法,建立了香精的指纹图谱,利用夹角余弦和欧式距离法计算相似度。结果表明:利用热脱附技术能够简化样品预处理过程,保证试验的重复性,为建立指纹图谱提供可靠的数据,并避免样品预处理过程中有效成分的损失以及高沸点物质对色谱仪器的污染。夹角余弦法和欧氏距离法计算简单,两者结合能够全面考察香精的质量。     

A Sensitive Method for Methyl tert-Butyl Ether Analysis in Water Samples by a New HS-SPME Vial and GC

In this study, a new sample vial has been designed for the extraction and determination of methyl tert-butyl ether (MTBE) in water samples by headspace solid-phase microextraction method. The special feature of this new vial is cooling the HS above the aqueous sample by cold water stream for maximum analyte absorption on SPME fiber coating. The analysis was by a gas chromatograph equipped with flame ionization detector and a capillary column (CP-sil 13 CB). Some significant variables affecting the extraction procedure were optimized. By use of divinylbenzene/carboxen/polydimethylsiloxane fiber, a sample volume of 10 mL, stirring rate of 1,000 rpm, salt concentration of 24%, extraction time of 15 min and extraction temperature of 83 °C, detection limit of 0.022 μg L⁻¹ and a good linearity (R ² = 0.998) in a calibration range of 0.1–400 μg L⁻¹ were achieved. The relative standard deviation for triplicate runs ranged between 6 and 8%. The method could be applied to the analysis of trace levels of MTBE in various water samples.

     

A Sensitive Method for Methyl tert-Butyl Ether Analysis in Water Samples by a New HS-SPME Vial and GC

In this study, a new sample vial has been designed for the extraction and determination of methyl tert-butyl ether (MTBE) in water samples by headspace solid-phase microextraction method. The special feature of this new vial is cooling the HS above the aqueous sample by cold water stream for maximum analyte absorption on SPME fiber coating. The analysis was by a gas chromatograph equipped with flame ionization detector and a capillary column (CP-sil 13 CB). Some significant variables affecting the extraction procedure were optimized. By use of divinylbenzene/carboxen/polydimethylsiloxane fiber, a sample volume of 10 mL, stirring rate of 1,000 rpm, salt concentration of 24%, extraction time of 15 min and extraction temperature of 83 °C, detection limit of 0.022 μg L^?1 and a good linearity (R ² = 0.998) in a calibration range of 0.1–400 μg L^?1 were achieved. The relative standard deviation for triplicate runs ranged between 6 and 8%. The method could be applied to the analysis of trace levels of MTBE in various water samples.     

A Versatile GC Method for the Analysis of Alkylglycerols and Other Neutral Lipid Classes

The present study focuses on the GC analysis of alkylglycerols and other neutral lipid classes. For that matter, a simple and rapid method based on the direct on-column injection has been developed for the simultaneous analysis of numerous fatty samples from different sources. Chemical transformation or treatment of the sample before the injection of samples is not required. In addition, quantification of different lipid classes was also evaluated with satisfactory results. Excellent results regarding reproducibility and resolution were observed. This method can be utilized for multiple purposes such as analyses of edible oils, shark liver oils, deodorizer distillates, time course analyses of lipase-catalyzed reactions, etc.     

色谱指纹图谱在香精香料质量控制中的应用

烟用香精香料化学成分复杂,现无合适的化学质量控制方法,通过实例,对10个批次正常生产的香料标样进行同时蒸馏萃取,取其萃取液进行气相色谱氢焰检测.进行同组分色谱峰的匹配,根据相对峰面积求出标准指纹图谱,然后10批标样各自与标准指纹图谱进行相似度计算,据此设立待测样品的合格性允差范围.待测样品与标准指纹图谱进行谱峰匹配,计算与标准指纹图谱的相似度,依据合格性允差范围,判定其质量状况.     

Studies of Radical Alternating Copolymerization. III. Kinetics of the Copolymerization of Citraconic Anhydride and Vinyl Acetate: A New Method of Evaluating the Kinetics Constant

We show that the copolymerization of citraconic anhydride and vinyl acetate is an alternating one. The two monomers form a charge transfer complex, and we propose a new strategy to determine the value of the velocity constants β₁ = K_AC/K_AD and β₂ = K_DC/K_DA involving the acceptor A, the donor D, and their charge transfer complex C. We obtained β₁ = 9.9 and β₂ = 3.6. The complex exhibits a greater reactivity than the monomer in the propagation reactions.     

一种新的化合物指纹及其在药物筛选中的应用

相似性搜索技术在大规模药物筛选中有着广泛的应用, 而作为其构成要素之一的化合物描述符, 则在相似性搜索中起着至关重要的作用. 但是迄今为止, 尚未发现一种描述符能够全面的描述化合物. 近来, 融合不同结构描述符用于相似性搜索的研究屡见报道, 不过由于这些描述符都源自化合物的结构, 融合以后不仅不能保证对化合物进行更全面的描述, 还带来严重的冗余现象. 为此, 根据哲学中对于一个事物的描述需要同时从本质与外延两个方面同时进行这一基本原理, 构建了一个全新的化合物活性描述符: 基因功能模块指纹(GO指纹), 综合运用结构指纹(本质)和GO指纹(外延)来描述化合物. 与将化合物基因表达直接构建的活性指纹不同, GO指纹不仅(1)降低了芯片数据的维度, 避免了其维度高、相关性强、噪声大的问题; 同时(2)拉近了描述符和化合物活性之间的距离. 通过将GO指纹和结构指纹融合后用于化合物相似性搜索, 结果表明新的描述符(1)使得结构和功能都相似的化合物之间的相似性更高; (2)而使得仅在单方面相似性较高的化合物得到有效排除. 本研究为进行快速、高效、大规模的药物筛选提供了新的思路, 这势必将提高药物筛选的结果, 进一步加快新药研发和旧药新用的进程.     

Effect of Wax Composition and Shear Force on Wax Aggregation Behavior in Crude Oil: A Molecular Dynamics Simulation Study

To explore the influence of different wax components and the shear effect exerted by the pump and pipe wall in the process of crude oil pipeline transportation on the microbehavior of wax aggregation in crude oil at low temperatures, molecular dynamics models of binary and multivariate systems of crude oil with different wax components are established in this paper. The simulation results are compared with the existing experimental results and the NIST database to verify the rationality and accuracy of the models. By using the established binary model to simulate four crude oil systems containing different wax components, it can be found that the longer the wax molecular chain, the more easily the wax molecules aggregate. The influence of temperature on the aggregation process of wax molecules with different chain lengths is also studied. The lower the temperature, the greater the difference in wax molecular aggregation degree caused by the difference in molecular chain length. Nonequilibrium molecular dynamics is used to simulate the shear process of a multivariate system of crude oil, and the micromechanisms of the shear effect on the aggregation process of wax molecules are studied. Shearing can destroy the stable structure of crude oil, resulting in the orientation and conformational transformation of wax molecules, and obtaining the region of wax molecules sensitive to temperature and shear effects, the temperatures of which are below the wax precipitation point and the shear rate of which is lower than the maximum shear rate to prevent the molecular structure from being destroyed. At the same time, the sensitivity of wax components with different chain lengths to the shear effect is studied. The research results provide theoretical guidance for ensuring the safe and economic operation of waxy crude oil production.     

对称群标准表示矩阵计算新方法

在多体问题的对称群方法中,群表示矩阵的计算是关键性问题。Young-Yamanouchi规则给出了标准正交表示的计算方法,然而该法相当繁琐,颇难使用,本文将2列Young表标准表示的计算方法[1]推广到任意不可约表示,给出对称群标准表示矩阵计算新方法.     

钛粉质量鉴定新方法试验研究

钛粉质量鉴定一直是用化学分析测定全钛含量，而不能确定单质态的钛含量，实验表明用Ｘ射线衍射分析鉴定钛粉质量效果较好，避名了化学分析的缺点，是一种值得推广的鉴定方法。     

The Transmutation of Wax: A Lesson in Experimental Design and Controls

The need for controls in experimental science is a difficult concept for many science students to grasp. To illustrate its importance, we developed an activity in which students, acting in the role of alchemists, perform an uncontrolled transmutation experiment. When their experiment yields a surprising result, the students are forced to recognize the critical role that a control plays in experimental design. The activity is constructivist in nature and engaging for students. Additionally, it offers the opportunity to introduce multicultural issues and topics from the history of science.     

A New Method for the Synthesis of gem-Dihydroperoxides

The tungstic acid-catalyzed reaction of ketals with hydrogen peroxide provides a convenient and efficient method for preparing gem-dihydroperoxides.     

A New Method for the Synthesis of Oligo-peptides

It was discovered that polypeptides were formed by self-assembly of N,O-bis(trimethylsilyl)amino acids with the assistance of O-phenylene phosphorochloridate.^[1] There were three steps involved in the self organization reactions, the activation of amino acid, the elongation of peptide chain and the termination of the chain reaction,among which the activation of amino acid -the formation of imino (alkyl)acetoxyphosphoranes was the key step. The formation process of the penta-coordinated phosphorus intermediates was showed in scheme 1.^[2,3,4] Through further studies of the mechanism of self-assembly reaction, it was found that carbonyl groups of the intermediates attacked by the neuclophilic groups were direct reson of the formation of peptides. However, the peptides in the solution were very difficult to be separated and analyzed.     

A New Method to Measure Thresholds of Electron-Stimulated Desorption: Modulation Method1

A new method to measure thresholds of electron-stimulated desorption (ESD) for neutral particles by means of energy-modulated electron beams is introduced. As examples of this new method, thresholds of ESD for neutral particles of N₂ and O₂ from the surfaces of polycrystalline Ni, Mo, and W are measured. Compared with the method via non-modulated electron beams, the instrument of measurement is simplified. Moreover, thresholds of ESD can be directly measured in high vacuum.