A High-Performance Liquid Chromatography Assay for Yohimbine HCl Analysis

The analysis used yohimbine HCl solution prepared from commercially available yohimbine HCl powder. Stability-indicating high-performance liquid chromatographic (HPLC) assay procedures were established and utilized to analyze the concentration of the drug. The method proved to be a simple model since it does not contain a buffer system. The mobile phase used, a methanol: 70:30 ratio, was similar to that suggested by the manufacturer for the storage of the column. Therefore, the solvent system saves analytical processing time since it does not require a change in the mobile phase before and after the analysis. The analytical method has been shown to be stability indicating. The assay method showed a retention time for yohimbine of 4.2 min; for caffeine, the internal standard, it was 2.3 min. The standard deviation and the coefficient of variation were under acceptable limits of 2% and were specifically 1.51% and 1.35% for within-day and between-day samples, respectively. The results showed that the degradation products obtained from stressing yohimbine HCl by heat and extremes in pH did not interfere with the yohimbine HCl peak, although the internal standard, caffeine, did show some interference due to having a retention time similar to the degradation products.     

The Influence of Drug-Excipient and Drug-Polymer Interactions on Butt Adhesive Strength of Ranitidine Hydrochloride Film-Coated Tablets

ABSTRACT

The influence of fillers and polymeric films on adhesive strength of hydroxypropyl methylcellulose (HPMC) and Eudragit E100® films coated on ranitidine HCl tablets containing either spray-dried rice starch (SDRS) or lactose monohydrate as fillers after storage at 45°C/75% RH for four weeks was investigated by the use of butt adhesion technique. The adhesive strength of film-coated tablets of fillers without drug was found to slightly decrease after storage. In contrast, the adhesive strength of drug-containing film-coated tablets significantly reduced, the degree of which was higher for Eudragit E100® than HPMC. Physicochemical characterization by employing differential scanning calorimetry (DSC) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the drug was obviously incompatible with lactose and possibly mild interaction with Eudragit E100® was suggested. The results indicated that the adhesive strength of film-coated tablets would be affected not only by the drug-excipient interaction, but also by the drug-polymeric film interaction.     

Formulation and In Vitro Studies of a Fixed-Dose Combination of a Bilayer Matrix Tablet Containing Metformin HCl as Sustained Release and Glipizide as Immediate Release

The emerging new fixed dose combination of metformin hydrocholride (HCl) as sustained release and glipizide as immediate release were formulated as a bilayer matrix tablet using hydroxy propyl methyl cellulose (HPMC) as the matrix-forming polymer, and the tablets were evaluated via in vitro studies. Three different grades of HPMC (HPMC K 4M, HPMC K 15M, and HPMC K 100M) were used. All tablet formulations yielded quality matrix preparations with satisfactory tableting properties. In vitro release studies were carried out at a phosphate buffer of pH 6.8 with 0.75% sodium lauryl sulphate w/v using the apparatus I (basket) as described in the . The release kinetics of metformin were evaluated using the regression coefficient analysis. There was no significant difference in drug release for different viscosity grade of HPMC with the same concentration. Tablet thus formulated provided sustained release of metformin HCl over a period of 8 hours and glipizide as immediate release.     

两套氯化氢合成及盐酸装置比较

对河南神马氯碱发展有限责任公司10万t/a和20万t/a烧碱配套HCl合成及盐酸装置的工艺、自动控制方案和运行情况进行比较,结果表明:10万t/a烧碱配套HCl合成及盐酸装置的手动操作占优势,20万t/a烧碱配套HCl合成及盐酸装置的占地面积、人员配置、自动控制方面占优势。     

Silicate-based polymer-nanocomposite membranes for polymer electrolyte membrane fuel cells

Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion^® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion^® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties.     

Probabilistic simulation of cable performance and water based protection in cable tunnel fires

Nuclear power plants contain a significant amount of fire load in form of electrical cables. The performance of the cables is interesting both from the fire development and system failure viewpoints. In this work, cable tunnel fires are studied using numerical simulations, focusing on the fire spreading along power cables and the efficiency of the water suppression in preventing the cable failures. Probabilistic simulations are performed using Monte Carlo technique and the Fire Dynamics Simulator (FDS) as the deterministic fire model. The primary fire load, i.e. the power cables are modelled using the one-dimensional pyrolysis model, for which the material parameters are estimated from the experimental data. Two different water suppression systems are studied. The simulation results indicate that using either suppression system decreased the heat release rate in the tunnel to less than 10% of the non-suppressed case. Without water suppression, the cables of the second sub-system were damaged in almost all fires, but when either of the studied water suppression systems was used, the probability of the cable failures was decreased to less than 1%. This result indicates that in current scenario, the probability of losing both sub-systems is determined directly by the suppression system unavailability.     

Distribution Behavior of Nb,Ta, and Pa as Homologues of Db in Cation Exchange and Solid-Liquid and Liquid-Liquid Extractions by Aliquat 336 from Hydrochloric Acid

Detailed chemical studies on transactinide elements will clarify their characteristic properties caused by strong relativistic effect. In this work, to realize chemical study on transactinide element ₁₀₅Db, cation exchange, and solid-liquid and liquid-liquid extractions of micro amounts of Nb, Ta (homologues of Db), and Pa (pseudo homologue) by Aliquat 336 were performed employing hydrochloric acid. Clearly different chloride complex formations and distribution reaction kinetics were observed among these elements, and the present results are useful for studying the chemical properties of Db. Based on these results, we propose suitable experimental conditions for Db.     

Highly Efficient Extraction of Rhodium(III) from Hydrochloric Acid Solution with Amide-Containing Tertiary Amine Compounds

Extraction of Rh(III) from a HCl solution with N,N-disubstituted amide–containing tertiary amine (ACTA) compounds (N,N-di-n-hexyl(N-methyl-N-n-octyl-ethylamide)amine (MonoAA), N-n-hexyl-bis(N-methyl-N-n-octyl-ethylamide)amine (BisAA), and tris(N-methyl-N-n-octyl-ethylamide)amine (TrisAA)) was investigated. The ACTAs extract Rh(III) more efficiently than tri-n-octylamine (TOA), and the extraction efficiency increases with increasing number of amide groups: TrisAA > BisAA > MonoAA ? TOA. For all ACTAs, the predominant Rh(III) complex extracted from 2 M HCl is probably {[RhCl₅(H₂O)]·(ACTA·H)₂}. The apparent basicity of the ACTAs and TOA varies in the opposite order from that observed for the Rh(III) extraction efficiency. Rh(III) can be readily back-extracted using 10 M HCl solution possessing a high selectivity over similarly loaded Pd(II) and Pt(IV).     

Third Phase Formation in the Solvent Extraction System Ir(IV)—Cyanex 923

Abstract

The splitting of a system from biphasic to triphasic was studied in the liquid‐liquid extraction of Ir(IV) and HCl using Cyanex 923 (C923). The limiting organic concentrations (LOC) of Ir(IV), which are the maximum possible concentrations of Ir(IV) in the organic phase without the formation of a third phase, were determined under different experimental conditions. The experimental conditions investigated were: concentrations of HCl and NaCl in the aqueous phase, concentrations of C923 and a modifier (tributyl phosphate (TBP) or decanol) in the organic phase, and an organic phase made with different diluents such as n‐octane, n‐nonane, n‐dodecane, kerosene, cyclohexane, toluene, and xylene. The formation of a third phase depends on the concentration of Ir(IV) and HCl in the aqueous phase, as well as on the other experimental conditions. The third phase appeared without Ir(IV) when the concentration of HCl in the equilibrated aqueous phase was 3.5 M and the organic phase contained 10% (v/v) C923/kerosene. The maximum LOC of Ir(IV) was obtained when the initial concentration of HCl in the aqueous phase was 2 M. The LOC of Ir(IV) can be increased though the addition of typical solvent modifiers (such as TBP or decanol) in the organic phase. The LOC of Ir(IV) varied significantly when it was extracted from an aqueous solution containing different concentrations of NaCl. The values obtained for the LOC using different diluents were in the following decreasing order: toluene ≈ xylene>cyclohexane>n‐octane>n‐nonane>kerosene>n‐dodecane. No third phase was detected when toluene and xylene were used as diluents. In the case of cyclohexane, no third phase was observed when the aqueous phase contained 4 M HCl. Spectral studies were performed to investigate the chemical composition of the third phase obtained with Ir(IV)‐HCl‐C923.