Determination of the purity of phenoxymethylpenicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica column

A micellar electrokinetic chromatographic and a fast reversed‐phase liquid chromatographic method have been developed for determination of the purity of phenoxymethylpenicillin. The optimized running buffer composition was 40 mM phosphate–borate–125 mM SDS–3.5% (v/v) methanol. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 3.5, and ACN, the flow‐rate being 3.5 mL/min. Both methods were successfully validated. Linearity, intermediate precision, limits of quantitation, accuracy, and a good correlation of the HPLC and MEKC results were demonstrated. Both methods proved to be fast and reliable and sufficiently sensitive. A combination of the two methods can be very useful in impurity profiling.     

The preparation of thick-film glass capillary columns

A detailed method for the routine preparation of glass capillary columns is presented. The method consists of coating a glass tube with quartz powder prior to pulling the tube into a capillary. The inner surface of the capillary consists of an even distribution of quartz particles fused to the walls. This surface has been found readily deactivated by standard procedures and ideal for the preparation of thick-film glass capillary columns. The method has been thoroughly tested in two independent laboratories to ensure that the procedures described are reproducible.     

CFRP-钢管-CFRP复合钢管约束海砂混凝土短柱轴压试验

以钢管壁厚、钢管屈服强度、碳纤维增强聚合物(carbon fiber reinforced polymer, CFRP)层数和位置、混凝土强度等为研究参数,进行19根CFRP-钢管-CFRP复合钢管约束海砂混凝土短柱的轴压试验,分析试件破坏模式、荷载-应变曲线、结构承载力等,并讨论现有算法对承载力计算的适用性.研究结果表明：内外壁CFRP与钢管的组合对核心混凝土有良好的复合约束作用,可大幅提高结构承载力;钢管内外壁张贴CFRP后,其结构破坏模式由剪切破坏变为腰鼓破坏;钢管最先开始屈服,CFRP层数决定纤维布的断裂宽度和分布;荷载-应变曲线在强化阶段呈明显线性上升特性,二次刚度由CFRP层数决定;与外壁张贴CFRP试件相比,内壁张贴CFRP试件的结构承载力更大.     

钢管混凝土组合柱耐火性能对比分析

采用非线性有限元软件ABAQUS对方钢管混凝土柱、复式钢管混凝土柱、内嵌十字型钢钢管混凝土柱和4腔钢管混凝土柱4种钢管混凝土组合柱开展火灾下的力学分析,并采用相关实验数据进行验证.分析不同荷载比下钢管混凝土组合柱的温度场、位移-时间曲线、截面内力重分布等.结果表明：内嵌型钢(钢管)有助于提升柱体的轴向刚度,钢管混凝土组合柱的破坏模态表现为压缩鼓曲破坏;低荷载比下内嵌钢管允许方钢管发生更高的温度材性劣化,进而提升了柱体的耐火性能,火灾荷载比越小,提升效果越显著.     

硫酸钡改性新型甲基化环糊精毛细管色谱柱柱行为的研究

在硫酸钡微晶对毛细管内壁改性的基础上,系统制备了甲基环糊精与不同混合固定液的毛细管色谱柱,从柱的分离选择性,惰性,柱效和分析准确性等方面作了较为系统的研究,并对环糊精的分离机理作了初步探索。     

Reaction of 2,6-dibenzylidenecyclohexanone with phosphorus pentachloride: Triple functionalization of the isosemiquinoid system

The reaction of 2,6-dibenzylidenecyclohexanone with PCl₅ occursvia the sequential stages of desoxychlorination and substitutional phosphorylation to form (after oxidation, methoxylation, and hydrolysis on the surface of the chromatographic SiO₂ adsorbent) organophosphorus products of the 1-(a-chloro-, a-hydroxy-, or -alkoxy)benzyl-2-chloro-3-(-(dimethylphosphoryl)benzylidene)cyclobex-1-ene series.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 441–443, February, 1996.     

The theoretical basis of column chromatography in multicomponent separations. Part 2: Peak capacity. Column systems with good selectivity

The selectivity of a column system, S, defined by equation 28, includes a variation coefficient (β) of plate number with capacity ratio which has a large influence on the peak capacity, as shown in Fig. 18. Some typical chromatograms are given. In order to predict S for a column system from Kovat's Index, equations 40 and 41 are given to calculate the constant of the carbon number rule for squalane at different temperatures or for different stationary phases. The specific retention value of heptane on squalane at different temperatures can be calculated from equation 42. The nonpolarity index, defined by equation 43, was used to calculate the retention value of heptane on various stationary phases. In liquid chromatography, the order of elution may be reversed by changing the composition of the eluent on the same chemically bonded silica (manufactured in China). The linear relations between the log retention values of different kinds of solutes or of a single solute on the silicas of different surface areas when using the same eluent are given.     

Determination of rare earth elements in seawater by on-line column preconcentration inductively coupled plasma mass spectrometry

A home made column of commercially available iminodiacetate resin, Muromac A-1 (50–100 mesh) was used to concentrate rare earth elements (REEs) (15 elements: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in seawater. An automated low pressure flow analysis method with on-line column preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) is described for the determination of REEs in seawater. Sample solutions (adjusted to pH of 3.0) passed through the column. After washing the column with water, the adsorbed elements were subsequently eluted into the plasma with 0.7 M nitric acid. Calibration curves were accomplished by means of purified artificial seawater with a sample loading time of 120 s. Detection limits (DLs) of the on-line column preconcentration/ICP-MS by eight replicate operations were between 0.040 and 0.251 pg ml⁻¹ for REEs in the artificial seawater. The precision was less than 8.9% for REEs and one sample can be processed in 7 min using a 7 ml of sample. The proposed method was applied to determine REEs in coastal seawater of Hiroshima Bay, Japan.     

套索冠醚毛细管色谱柱的研制

用套索冠醚N,N′-双(2-甲基吡啶)-二氮杂-18-冠-6作为固定相,涂渍在弹性石英毛细管内,测其柱效、惰性、热稳定性、平均极性及选择性等性质.其结构由元素分析、红外光谱、核磁共振及质谱分析的试验数据所证实.试验表明,它具有良好的色谱性能、中等极性,适用于对醇、卤代烃、芳香烃等各类异构体的分离,并用分子结构观点探讨了保留机理.     

分子筛改性气—液毛细管柱及其性能考察

以原位合成法制备的分子筛膜对玻璃毛细管内壁进行改性后，成功地制备了常规口径及大口径分配ＳＣＯＴ柱，并对毛细管柱的性能进行了评价。