一清颗粒中黄芩薄层色谱法的改进

一清颗粒中黄芩薄层色谱的改进,展开剂;醋酸乙酯-丙酮-甲酸-水(26:7:1.5:3),分离效果好,斑点清晰,重复性好。     

研究止咳枇杷颗粒的微乳薄层色谱鉴别

目的探讨微乳薄层色谱法在止咳枇杷颗粒鉴别中的应用。方法以SDS正丁醇正庚烷水微乳液作为展开剂，通过聚酰胺薄层层析，分离和鉴别了止咳枇杷颗粒中的百部、桑白皮、白前3种药材，考察了微乳液类型、改性剂、酸度等因素对分离效果的影响。结果百部的鉴别以含水量9似微乳液甲酸（9：1）为最佳展开剂，桑白皮、白前的鉴别以含水量70％微乳液甲酸（9：1）为最佳展开剂。结论微乳薄层鉴别斑点清晰，为止咳枇杷颗粒鉴别提供了一种简便、准确方法。     

海外文献速递

电　镀2 0 0 0 0 90 1　在甘氨酸介质中电沉积ＣｕＩｎＳｅ2 薄层———ＶｇａｒｔｅＲ .ＴｈｉｎＳｏｌｉｄＦｉｌｍｓ ,1999,34 0 ( 1) :117(英文 )在Ｔｉ和导电性玻璃基体上用含ＣｕＣｌ2 、ＩｎＣｌ3、ＳｅＯ2 的甘氨酸介质 (用ＨＣｌ将ｐＨ值调至 2左右 )动电位电沉积ＣｕＩｎＳｅ2 多晶薄层 ,研究了加入ＥＤＴＡ络合剂后的影响。获得的膜层经不同的后处理 ,在约 4 0 0℃的Ａｒ气中热处理 ,在 0 .5ｍｏｌ/ＬＫＣＮ溶液中刻蚀 ,室温空气氧化。考察了膜层处理后的特征 ,热处理提高了镀层的结晶度 ,使晶粒变粗 ,从而导致ＣｕＩｎＳｅ2 黄…     

5℃养护下甲酸钙对水泥早期水化的影响

本工作在5℃低温条件下,研究了甲酸钙对砂浆1d、3d、7d、28d抗压强度的影响规律,并分别从水化放热、水化动力学过程、水化产物等角度,分析了低温下甲酸钙对水泥早期水化的影响.结果表明:甲酸钙具有低温早强作用,可促进5℃低温下砂浆早期强度的发展,其强度提高作用时间主要在前3 d,适宜掺量范围为1％～2％.甲酸钙的掺入可促进低温下水泥初期(前7 d)的水化反应,使水泥水化诱导期略有缩短,加速期提前,水化温峰出现时间提前,水化放热速率、放热量均明显增大;掺甲酸钙组分可提高水泥水化结晶成核与晶体生长(NG)、相边界反应(I)和扩散反应(D)各阶段的反应速率,并使相边界反应(I)阶段持续时间延长、水化程度提高.水泥初期(前7 d)水化产物中Ca(OH)2数量增加,但水化产物种类未发生明显变化.     

温度和甲酸镍含量对制备Zn-Ni合金渗层的影响

为改善渗锌层的防腐性能，通过在渗锌过程添加甲酸镍制备了Zn-Ni合金渗层，分析了不同温度(400℃、450℃、500℃、550℃、600℃)和不同甲酸镍含量(0 g、15 g、44 g、75 g、103 g)对渗层制备过程的影响。采用扫描电镜(SEM,配备有EDS能谱)、X射线衍射仪(XRD)分析了不同试样渗层截面形貌和物相组成；采用电化学极化曲线和阻抗谱(EIS)表征了不同试样在3.5%(质量分数，下同)NaCl溶液中的电化学行为，并通过中性盐雾实验测试了渗层的耐蚀性能；利用显微维氏硬计测试渗层表面至基体不同相层硬度。结果表明：随温度的升高渗层显著增厚，渗层表面硬度降低；随甲酸镍含量的增加渗层明显减薄，渗层中ZnO、Fe₃ZnC_0.5相衍射峰明显增强，渗层中间相层硬度值增大；温度和甲酸镍含量对渗层自腐蚀电位无明显影响，腐蚀电流密度随温度的升高而增大，随甲酸镍含量的增大而明显减小；试样阻抗弧半径和渗层电阻均随甲酸镍含量的增加而增大；甲酸镍含量越高，对盐雾实验白锈的出现抑制越明显，出现红锈的时间显著延长。综上所述，添加甲酸镍显著改善了渗锌层的组...     

二(3,5-二硝基苯甲酸)二甘醇酯的合成研究

文章以3,5-二硝基苯甲酸和二甘醇为原料,在钛酸四丁酯的催化条件下,合成了二(3,5-二硝基苯甲酸)二甘醇酯.正交试验结果显示,当酸醇的量比为2.05,催化剂的量为3,5-二硝基苯甲酸的0.95%,反应时间为100 min,带水剂的量占3,5-二硝基苯甲酸的35.5%,收率较高(90%),产物结果经IR、MS、H1NMR表征证实为目标化合物.     

汞灯辅助MOCVD SnO2薄层晶体的结构与透明导电性研究

采用x—射线衍射(XRD)、高能电子衍射(RHEED)、扫描电子显微镜(SEM)和紫外可见吸收谱(UV)等技术研究了在汞灯(ML)辅助下进行有机金属化学气相沉积(MOCVD)所得本征及掺杂SnO_2薄层晶体的结构和透明导电性。实验指出,采用汞灯辅助有机金属化学气相沉积(ML-MOCVD)SnO_2薄层晶体比无汞灯辅助的有机金属化学气相沉积(MOCVD)膜层生长速度快,结晶粒度大且其透明导电性能更好。本文对ML-MOCVD SnO_2薄层晶体的结晶粒度与生长温度的关系、掺杂对结晶取向的影响以及可见光透过率、导电性能等进行了较详细的研究。结果指出,ML-MOCVD是获得透明导电优质薄层SnO_2晶体材料的最佳途径。     

直接甲酸燃料电池阳极电催化剂研究获进展

正近日,中科院长春应化所研究员邢巍课题组与瑞士巴黎高等洛桑联邦理工学院胡喜乐教授带领的科研团队开展国际合作,成功设计并制备了直接甲酸燃料电池(DFAFC)高效阳极非铂催化剂。直接甲酸燃料电池,因其制作程序简单、比能量和比功率高,是新一代移动和便携式电源。该技术是将储存于甲酸和氧气中     

Pd/MWCNT的合成及其对甲酸电化学氧化的催化性能

以多壁碳纳米管(MWCNT)为载体,用简单的液相还原法制备了金属载量为10%的碳载Pd催化剂(Pd/MWCNT)。X射线衍射(XRD)和透射电镜(TEM)分析结果显示Pd粒子结晶度较低,分布均匀,平均粒径为2.4nm,小于两种商业10%Pd/C催化剂。循环伏安测试结果表明Pd/MWCNT对甲酸氧化的催化活性最好,相同条件下甲酸氧化峰电流最大。极化曲线显示Pd/MWCNT电极的极化过电位和50mA/cm2下恒电流放电90分钟后的过电位都明显小于其他两种商业Pd/C催化剂,表明Pd/MWCNT催化剂对甲酸电化学氧化具有较好的催化活性和催化稳定性。     

新能源材料

正美国研发耐高温柔性太阳能电池转换效率达11.8%美国爱荷华州立大学的研究人员开发出一种柔性钙钛矿太阳能电池,其效率为11.8%,并具有较强的耐高温性。科学家使用逐层气相沉积技术,将碘化铅(PbI_2)和溴化铯(CsBr)前驱体的薄层制成了无机混合卤化物钙钛矿太阳能电池。研究人员指出,使用无机化合物(例如铯)有助于使电池具有更高的耐热性。他们称,在72h的X射线衍射分析中,该电池即使在200℃下也没有显示出热降解。(中国半导体行业协会)     

An Application of X-ray Fluorescence Spectrometry to the Study of Thin-Layer Chromatography

The combination of thin-layer chromatography (TLC) with X-ray fluorescence spectrometry (XRF) has been accomplished without any interfaces. It enables the direct, nondestructive visualization of elements developed on a TLC plate. In addition to inorganic compounds, organic compounds including electronegative elements can be detected simultaneously that cannot always be measured satisfactorily by competitive techniques; e.g., phenolic compounds containing chlorine, bromine, or iodine were distinctly detected by individual elemental imaging. The background of commercially available TLC plates with various thicknesses of the stationary phase and an outline of element detection limits were also investigated. TLC/XRF was found suitable for in situ TLC imaging of elements.     

Interfaces to connect thin-layer chromatography with electrospray ionization mass spectrometry

This study has developed two interfaces to connect small-size thin-layer chromatography (TLC) with electrospray ionization mass spectrometry (ES-MS) for the continuous analysis of organic mixtures. The interfaces are (1) two bound optical fibers inserted into the C18-bonded particles at the exit of a small TLC channel and (2) a small commercial TLC strip with a sharpened tip. A reservoir continuously supplied a makeup solution to the tip of the TLC channel. The high voltage required for electrospray ionization was introduced into the makeup solution or mobile phase through a Pt wire, and electrospray was generated at the tip of the bonded optical fibers and at the sharp end of the TLC strip. Since small-size TLC channels were used, the elution time was short and less than 0.2 microL of the sample solution and 200 microL of the eluting solvent were required. Organic mixtures were separated successfully and detected on-line using the TLC/ES-MS techniques.     

General contribution of nonspecific interactions to fluorescence intensity

Many chemical compounds, including nonfluorescent ones, induce changes in the fluorescence spectra of certain probes, such as berberine cation and Reichardt's betaine, both in the absence and the presence of solvent, that affect almost exclusively emission intensity. In this work, the application of fluorescence detection by intensity changes (FDIC) to HPLC and TLC chromatographic systems with fluorescence detectors has been studied. FDIC detection is of special interest in detecting nonfluorescent analytes, either in HPLC or in TLC mode. It does not involve covalent interactions, and the dielectric permittivity (epsilon) of the medium plays an important role. The balance between nonspecific and specific interactions produces either an increase or a decrease in fluorescence intensity. Therefore, the influence of chromatographic conditions and chemical structure of analytes on the sign and magnitude of fluorescence peaks for sample detection in HPLC and TLC systems has been discussed. In general, probe nature and concentration determine response and detection sensitivity for a given sample in TLC and HPLC. As solubility and fluorescence properties in solvents determine the operating conditions for a FDIC probe in HPLC mode, nature and flows of mobile phase and solvent are important for chromatographic response and detection sensitivity.     

Stability indicating TLC method for the quantification of tinidazole in pharmaceutical dosage form - I.V. Fluid

Tinidazole was separated from degradation products formed in large volume parenteral preparations by TLC method using Silica gel GF254 as stationary phase and Chloroform - Methanol (9:1) mixture as mobile phase. Subsequently extracted with ethyl alcohol and estimated by measuring absorbance at 310nm using standard calibration curve. Recovery was 98 to 102% and the co-efficient of variation was 2.1%.     

Stability indicating TLC method for the quantification of tinidazole in pharmaceutical dosage form - I.V. Fluid

Abstract

Tinidazole was separated from degradation products formed in large volume parenteral preparations by TLC method using Silica gel GF254 as stationary phase and Chloroform - Methanol (9:1) mixture as mobile phase. Subsequently extracted with ethyl alcohol and estimated by measuring absorbance at 310nm using standard calibration curve. Recovery was 98 to 102% and the co-efficient of variation was 2.1%.     

Apparatus and initial results for pressurized planar electrochromatography

Pressurized planar electrochromatography (PPEC) is a new planar chromatographic technique in which the mobile phase is driven by electroosmotic flow, while the sorbent layer is pressurized in a manner that allows heat to flow from the layer through an electrically insulating, thermally conducting, sheet of aluminum nitride ceramic. A prototype apparatus for performing PPEC is described. Separation by PPEC is faster than by conventional TLC, and an example is presented of a 24-fold enhancement in the speed of separation. PPEC was performed on both regular and high-performance C18 layers, and the latter yield substantially faster separation. The sorbent layer requires conditioning at elevated temperature before use, and solute migration velocity increases with this temperature. The flow rate increases in a linear manner with increasing voltage and diminishes in a nonlinear manner with increasing pressure. Both electrical current and Joule heating diminish with increasing pressure, and the diminution of flow at high pressure can be compensated by an increase in voltage. PPEC is more efficient than classical TLC. Theoretical plate heights diminish with increasing Rf and are in the range 29-21 and 55-27 microm for the high-performance and regular plates, respectively. PPEC retains the advantages of classical TLC but has the ability to separate a substantially higher number of samples simultaneously. An example is presented on the separation of nine samples in 1 min on a 2.5 cm x 10 cm sorbent layer.     

Stability Study of Lorazepam in Solid Dosage form by High Performance Liquid Chromatography

Abstract

A reverse phase column with MeOH-H₂0 as mobile phase and detection at 230 nm was employed for the determination of lorazepam and degradation products in tablet formulation. The mean coeficient variation (n=6) for the entire analytical method was 1.15%. A working calibration curve over a concentration range of 5 to 250 ng of lorazepam was obtained and the recovery (n=3) was 100.5%. Limits of detection varied from 1.6 to 3.2 ng according to the compounds. Natural and thermal stability of the drug and tablets were carried out since the method was suitable for stability indicating studies. A comparative TLC method was also performed. The effect of the type and concentration of acid and the content of methanol in reaction medium of hydrolysis of lorazepam were also investigated. Degradation products were characterized by HPLC and TLC by comparing them to authentic samples. The first degradation product that appeared was the quinazoline-carboxaldehide and 2-amino-2′,5-dichlorobenzophenone was not detected. The additives in tablets decreased drug stability and degradation pathway followed by the tablets was similar to the drug under thermal conditions.     

On-line overpressure thin-layer chromatographic separation and electrospray mass spectrometric detection of glycolipids

On-line thin-layer chromatographic separation and electrospray mass spectrometry (TLC/ESI-MS) has been accomplished by direct linking of a commercial overpressure TLC instrument, OPLC 50, and a Q-TOF mass spectrometer. Mass spectrometric detection sensitivity and chromatographic resolution achieved by this configuration were assessed using acidic glycolipids as examples. Under the optimized conditions, a sensitivity of 5 pmol of glycosphingolipid was readily demonstrated for TLC/ESI-MS and 20 pmol for TLC/ESI-MS/MS production scanning to derive the saccharide sequence and long chain base/fatty acid composition of the ceramide. Initial preconditioning of TLC plates is necessary to achieve high sensitivity detection by reducing chemical background noise. Plates can be used repeatedly (at least 10 times) for analysis, although this may result in a minor reduction in TLC resolution. Following solvent development, separated components on the TLC plates can be detected in the conventional way by nondestructive staining or UV absorption or fluorescence and can be stored for on-line TLC/ESI-MS analysis at a later stage without reduction in mass spectrometric detection sensitivity and chromatographic resolution. Aspects for further improvement of OPLC instrumentation include use of narrower TLC plate dimensions and refined design of the eluate exit system.     

Thin-layer chromatography and electrospray mass spectrometry coupled using a surface sampling probe

A combined surface sampling probe/electrospray emitter was used for the direct readout of thin-layer chromatography plates by electrospray mass spectrometry. The technique was demonstrated with reversed-phase C18 plates using a three-dye mixture composed of methylene blue, crystal violet, and rhodamine 6G for positive ion mode detection and a separate dye mixture containing fluorescein, naphthol blue black, and fast green FCF for negative ion mode detection. Acquisition of mass spectra of components of individual bands on the plate was shown by manual stepping to and sampling from specific locations within the bands. Computer-controlled scanning of development lanes on the plate was illustrated by using multiple ion monitoring in both positive and negative ion modes. Commercial TLC plates were used and no post-separation processing other than drying of the plates was required prior to mass spectrometric analysis. Readout resolution, the limits of scan speed, detection levels, TLC phase, and eluting solvents were investigated and discussed.     

A comparison of different ways to approximate time-to-line crossing (TLC) during car driving

Three experiments are presented in which the accuracy of different methods to approximate time-to-line crossing is assessed the first experiment TLC was computed, using a trigonometric method, during normal driving while the vehicle stayed in lane. The minima of TLC were compared with two approximations and it was found computing TLC as lateral distance divided by lateral velocity gave poor results. It was concluded that this simple approximation is not suitable for measuring TLC minima in studies of driver behaviour. A way of computing TLC that takes account of the curved path of the vehicle resulted in a good fit of TLC minima. In two other experiments the vehicle exceeded the lane boundary, either intentionally as a result of a lane change manoeuvre, or unintentionally as a result of impaired driving. In these cases no TLC minima exists since these only occur as a result of correcting steering actions to stay within the lane. In contrast to normal lane keeping, it was found that prior to crossing the lane boundary, the simple approximation resulted in more accurate estimation of available time before the lane boundary is exceeded compared to the more complex approximation. This indicates that for lane keeping support systems and systems that detect when the driver has fallen asleep and drifts out of lane, a simple algorithm for TLC estimation may give reliable results, while this algorithm is not accurate enough for more fundamental studies of driver behaviour. However, the reliability of the approximation is only satisfactory over a very short time range before the lane boundary is actual exceeded. This may result in warnings that come too late and result in too little time to respond for the driver.