Simultaneous determination of chlordiazepoxide and selected antidepressants using CZE

A simple CE method was developed and validated for the simultaneous determination of chlordiazepoxide (CHL), amitriptyline, and nortriptyline (mixture I) or the determination of CHL and imipramine (mixture II) using the same BGE. Sertraline and amitriptyline were used as internal standards for the first and second mixtures, respectively. The method allows amitriptyline to be completely separated from its impurity and main metabolite nortriptyline, which can be quantified from 0.2 μg/mL. The separation was achieved using 20 mM potassium phosphate buffer pH 5 containing 12 mM β‐cyclodextrin and 1 mM carboxymethyl‐β‐cyclodextrin. UV detection was performed at 200 nm and a voltage of 15 kV was applied on an uncoated fused‐silica capillary at 25°C. These experimental conditions allowed separation of the compounds to be obtained in 7 min. Calibration graphs proved the linearity up to 40 μg/mL for CHL, up to 100 μg/mL for amitriptyline and imipramine, and up to 5 μg/mL for nortriptyline. The accuracy and precision of the method have been determined by analyzing synthetic mixtures and pharmaceutical formulations. The analytical results were quite good in all cases indicating that the method was linear, sensitive, precise, accurate, and selective for both mixtures.     

One-Pot Synthesis of 1H-Benzimidazole Derivatives Using Thiamine Hydrochloride as a Reusable Organocatalyst

A simple and efficient one-pot synthesis of 1H-benzimidazole derivatives using thiamine hydrochloride (VB₁) as the organocatalyst from o-phenylenediamine and aldehyde in dimethylformamide is described. Compared to classical reaction conditions, this new method consistently has the advantages of excellent yields, metal-ion-free procedure, and good recovery and reusablity of catalyst.     

An Efficient One-Pot Synthesis of N-Methoxy-N-methylamides from Carboxylic Acids

Abstract

Several N-methoxy-N-methylamides were prepared by the reaction of the corresponding carboxylic acids with N,O-dimethylhydroxylamine hydrochloride at room temperature using trichloromethyl chloroformate in the presence of triethylamine in excellent yields.     

Preparation of Primary Thioamides From Nitriles Using Sodium Hydrogen Sulfide and Diethylamine Hydrochloride

Primary thioamides are prepared in moderate to excellent yields by treating nitriles with sodium hydrogen sulfide and diethylamine hydrochloride in an appropriate solvent with mild heating.     

Formulation and In Vitro Evaluation of Sustained Release Microspheres of Diltiazem Hydrochloride Prepared by Emulsification-Internal Gelation Method

The present work describes the formulation of alginate microspheres containing diltiazem hydrochloride by the emulsification-internal gelation method with the use of barium carbonate as a cross-linking agent. The effect of various factors (the concentration of alginate and barium chloride) on the drug loading efficiency and in vitro release were investigated. Fourier transform infrared microscopy (FTIR) and differential scanninig calorimetry (DSC) analysis confirmed the absence of any drug polymer interaction. X-ray diffraction (XRD) pattern showed that there is a decrease crystallinity of the drug. The in vitro drug release profile could be altered significantly by changing various processing parameters to give a controlled release of drug from microcapsules. The stability studies of drug-loaded microcapsules showed that the drug was stable at different storage conditions.     

Micellization and Clouding Phenomenon of Phenothiazine Drug Promethazine Hydrochloride: Effect of NaCl and Urea Addition

Herein we report the micellization and clouding behavior of promethazine hydrochloride (PMT) in absence and presence of NaCl/ureas. The critical micelle concentration (CMC) of PMT is measured by conductivity method and the values decrease with increasing the NaCl concentration. With increasing the temperature, the CMC first increases then decreases. At 25°C, the maximum CMC values were obtained (with or without NaCl). The thermodynamic parameters are evaluated which indicate more stability of the PMT solution in presence of NaCl. PMT shows phase separation also. The cloud point (CP) of PMT decreases with increase in pH due to deprotonation of the drug molecules. Ureas decreased the CP and the behavior is explained on the basis of removal of water from the head group region.     

A comparative study of two polymorphs of L‐aspartic acid hydrochloride

Two polymorphs of L‐aspartic acid hydrochloride, C₄H₈NO₄⁺·Cl⁻, were obtained from the same aqueous solution. Their crystal structures have been determined from single‐crystal data collected at 100 K. The crystal structures revealed three‐ and two‐dimensional hydrogen‐bonding networks for the triclinic and orthorhombic polymorphs, respectively. The cations and anions are connected to one another via N—H...Cl and O—H...Cl interactions and form alternating cation–anion layer‐like structures. The two polymorphs share common structural features; however, the conformations of the L‐aspartate cations and the crystal packings are different. Furthermore, the molecular packing of the orthorhombic polymorph contains more interesting interactions which seems to be a favourable factor for more efficient charge transfer within the crystal.     

纳米Ag/TiO_(2)纳米管阵列基底构建及表面增强拉曼散射光谱检测与降解盐酸四环素北大核心CSCD

将阳极氧化与光还原法结合,在TiO_(2)纳米管阵列(TiO_(2)NTAs)表面修饰Ag纳米粒子,获得一种均匀有序、稳定性高且可循环的TiO_(2)NTAs/Ag活性基底。采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)、表面增强拉曼散射光谱(SERS)和扫描电子显微镜(SEM)等手段对TiO_(2)NTAs/Ag的组成和结构进行了表征。进一步研究了该TiO_(2)-NTAs/Ag阵列对盐酸四环素(TC-HCl)的SERS响应,结果表明,该复合基底对TC-HCl具有较高的检测灵敏度,在水中检测限可达1×10^(−14) mol/L,而TiO_(2)-NTAs与Ag之间的协同效应对其检测性能的提高起着关键作用。此外,TiO_(2)NTAs/Ag基底在光照下对TC-HCl展示了优异的降解活性,且至少可循环使用8次。表明该TiO_(2)NTAs/Ag基底在环境中有机污染物的SERS检测和降解领域具有潜在的应用前景。