Analysis of dissolution test sample solutions by high speed capillary electrophoresis

Summary The quantitative use of high speed capillary electrophoresis (HSCE) is examined by applying high voltages across short capillaries. Acceptable performance in terms of injection precision and migration times were achieved within 1–2 minute analysis times. HSCE was used for the novel CE application of dissolution test sample solution analysis. The results generated by HSCE compared well with those generated using validated on-line UV absorbance measurements. It is concluded that HSCE is a viable alternative and supplement to standard analytical methods employed in dissolution test analysis.     

高速毛细管电泳技术

高速毛细管电泳技术(HSCE)的特点在于通过增大分离高压和缩短毛细管,将分析速度提高到几秒至几分钟内;近几年HSCE得到了较大的发展;本文着重介绍了高速毛细管电泳技术的理论、进样方法、检测器及其在各个领域的应用。     

Passive broadband reflector using photocrosslinkable liquid crystal molecules

This work consists in creating passive optical filter reflecting light in a broadband wavelength with photo‐polymerizable mesogenic liquid crystal (LC) molecules from a reproducable method. The influence of several parameters was studied and it appears that reflective wavelength range can be modified by chiral agent concentration and/or temperature. Band broadening is influenced by several process parameters such as layer thickness, polymerization and dissolution times. A semi‐quantitative analysis allows the variation of conversion ratio as a function of polymerization and dissolution times to be determined. Copyright © 2002 John Wiley & Sons, Ltd.     

高速毛细管电泳安培法检测甲巯咪唑及其制剂

采用高速毛细管电泳安培法对甲巯咪唑(TMZ)及其制剂的测定进行了研究; 通过优化检测电位、毛细管长度和内径、分离电压、缓冲溶液等实验参数, TMZ在60 s内可以得到较好的分离, 线性范围在2.00×10-3～2.80×10-5 mol/L, 检出限为3.50×10-6 mol/L; 峰面积和迁移时间的相对标准偏差分别为2.7%、 1.2% (n＝8); 该法可用于制剂中TMZ的检测.     

Direct observation of cellulose dissolution in subcritical and supercritical water over a wide range of water densities (550–1000 kg/m<Superscript>3</Superscript>)

Direct observations of the heating of microcrystalline cellulose (230 DP) in water at temperatures up to 410 °C and at pressures up to 700 MPa were made with a batch-type microreactor. Cellulose particles were found to dissolve with water over temperatures ranging from 315 to 355 °C at high pressures. Dissolution temperatures depended on water density and decreased from about 350 °C at a water density of 560 kg/m³ to a minimum of around 320 °C at a water density of 850 kg/m³. At densities greater than 850 kg/m³, the dissolution temperatures increased and reached a value of about 347 °C at 980 kg/m³. The cellulose dissolution temperatures were independent of heating rates for values ranging from 10 to 17 °C/s. The low dependence of dissolution temperatures on the heating rates is strong evidence for simultaneous dissolution and reaction of the cellulose. Different phenomena occurred depending on water density. At low densities, particles turned transparent and seemed to dissolve into the aqueous phase from the surface. From 670 to 850 kg/m³, the cellulose particles visibly swelled just before completely collapsing and dissolving into the aqueous phase. The swelling probably increased water accessibility and particle surface area and thus lead to the lower dissolution temperatures observed. From 850 to 1000 kg/m³, the particles required longer times to dissolve and many fine brown-like particles were generated as the particles dissolved. FT-IR spectra of the residues were analyzed. Residues formed from heating cellulose at high densities still retained some cellulose character whereas those as low densities had little cellulose character, especially in the O–H stretching vibration region.     

Thermodynamic and kinetic properties of <Emphasis Type="Italic">cis</Emphasis>-diammineglycolatoplatinum in different water solvents

The dissolution behavior of cis-diammineglycolatoplatinum (nedaplatin) in saline, water and glucose were studied by a microcalorimetric method. The integral heats and differential heats of the dissolution were measured to establish the equation for the solute and the heats. The corresponding half-life, kinetic and thermodynamic properties of the nedaplatin solutions were determined. The results show that hydrogen bonds could be generated and the dissolution entropy of nedaplatin in different solvents is negative during the dissolution process, so as to enhance the drug stability, but there is an obvious difference in stability in different solvents.     

Investigation by electrochemical and deflectometric techniques of silicon dissolution and passivation in alkali

The effects of anodic polarization of p-Si electrodes in alkaline medium have been investigated by the probe beam deflection (PBD) or `mirage' technique and the optical cantilever or bending beam method (BBM). The PBD technique permits a monitoring of dissolution and passivation processes and provides an estimate of the oxide etchback times during open circuit corrosion. The BBM technique has been used to estimate the stress of the thin oxide layer, which appears to be in the order of 180 MPa for very thin oxide films (nm range). The result is discussed in comparison with literature properties of thermally generated oxides.     

Determination of nitrogen in UO2 by Kjeldahl spectrophotometry

A method for the dissolution of sintered UO₂ samples and the determination of ammonium ions in the solution by spectrophotometry for the chemical quality control of UO₂ fuel for nitrogen is described. The acid mixture used simplifies the problem of recovery of uranium from the waste generated during the analysis of nitrogen. Nitrogen content in ppm in the sintered UO₂ samples is determined within an RSD of 10%.     

Inclusion Complexation of Anti-HIV Drug with β-Cyclodextrin

The purpose of present investigation was to investigate the effect of complexation of Nelfinavir Mesylate (NM) – an Anti-HIV drug with Beta-cyclodextrin (β-CD) on its dissolution characteristics and subsequent effect on its absorption properties and bioavailability. Phase solubility studies were conducted to find the interaction of NM with β-CD. Physical mixing and milling method were used for complexation. The inclusion complexes were characterized by X-ray diffractometry, FT-IR and NMR studies and further studied by in-vitro dissolution testing. The plain NM and complex was subjected to intestinal absorption studies by using Everted intestinal sac model. Data was treated statistically by Mann–Whitney U test. Pharmacokinetic studies were carried out in rabbits using cross over design and data was treated by Student’s t test. Phase solubility studies confirmed 1:1 complex formation of NM with β-CD with stability constant of 204.84 M⁻¹. In-vitro dissolution studies of inclusion complexes of NM with β-CD prepared by milling method (T ₉₀=60.89 min) showed better dissolution rate kinetics in distilled water in comparison with plain NM (T ₉₀=374.31). The increased solubility with decreased crystallinity is attributed by inclusion of NM in the cavity of β-CD, which was further confirmed by instrumental studies. Intestinal absorption studies further supports these findings by showing 2.13 times enhancement in the absorption rate of complex as compared to plain NM. The percent relative bioavailability of complex in rabbits was 185.37 as compared to the plain NM.     

Relationship between dissolution rate of uranium dioxide pellets in nitric acid solutions and their porosity

Dissolution of uranium dioxide pellets /10 mmø×11 mm/ in nitric acid was studied. A dependence of the initial dissolution rate on acid concentration and temperature was observed. The effective surface area of the pellet was measured during the dissolution process, and compared with its apparent surface area. The experimental dissolution curve was in good agreement with the curve obtained by simulations assuming that the dissolution rate depends on the effective surface area.     

Chemometrics-assisted simultaneous determination of atenolol and chlorthalidone in synthetic binary mixtures and pharmaceutical dosage forms

Resolution of binary mixtures of atenolol (ATE) and chlorthalidone (CTD) with minimum sample pre-treatment and without analyte separation has been successfully achieved, using a new and rapid method based on partial least squares (PLS1) analysis of UV spectral data. The simultaneous determination of both analytes was possible by PLS1 processing of sample absorbances between 255 and 300 nm for ATE and evaluation of absorbances in the 253–268 nm region for CTD. The mean recoveries for synthetic samples were 100.3±1.0% and 100.7±0.7% for ATE and CTD, respectively. Application of the proposed method to two commercial tablet preparations in the content uniformity test showed them to contain 103.5±0.8% and 104.9±1.8% ATE respectively, as well as 103.4±1.2% and 104.5±2.2% CTD. Use of this method also allowed the elaboration of dissolution profiles of the drugs in two commercial combined formulation products, through the simultaneous determination of both drugs during the dissolution test. At the dissolution time of 45 min specified by USP XXIV, both pharmaceutical formulations complied with the test.     

Effect of hydrogen sulfide on the iron dissolution rate in a sodium sulfate solution under natural aeration conditions

The influence of hydrogen sulfide (10–100 mg/1) on the Armco iron anodic dissolution in an aerated 0.17 M Na₂SO₄ solution is investigated. During a potentiostatic anodic polarization, the hydrogen sulfide introduction makes the current increase stepwise. The magnitude of the increase depends on the duration of preliminary anodic polarization, electrode potential, and hydrogen sulfide concentration. The anodic metal dissolution activation by hydrogen sulfide is explained by chemical conversion of the oxide-hydroxide passivating film into iron sulfide that is generated at the metal surface in the form of a porous film and does not hinder the electrode dissolution. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.     

Effect of milled fluidised bed cracking catalyst waste on hydration of calcium aluminate cement and formation of binder structure

The effect of Bi addition on precipitation and dissolution, in Cu–9at% In and Cu–5at% Sb supersaturated solid solutions, has been studied by several complementary techniques. Differential Dilatometry and Differential Scanning Calorimetry permit only the analysis of the δ phase dissolution kinetic in sufficiently aged samples. Delayed spheroidization due to Bi segregation around the precipitated lamellae, observed by Transmission Electron Microscopies in the first alloy, gives a residual interfacial energy leading to accelerated δ phase dissolution with decreased activation energy. Kinetics parameters evolution indicates a progressive δ phase continuous dissolution which makes available a small chemical driving force at high temperatures and leads to an increasing activation energy during dissolution. However, Bi dispersed particles in the second alloy haven’t effect on the dissolution but they cause a contraction above 833 K. Kinetics parameters evolution indicates rapid δ phase dissolution that shifted to high temperatures where an important chemical driving force for solution treatment is available. It leads to almost constant activation energy.

     

Formulation approach for nicorandil pulsatile release tablet

The purpose of this study was to obtain a nicorandil pulsatile release tablet that has a well-regulated release lag time. When nicorandil is used as an antiangina drug, administration time control is important. A pulsatile release tablet is one of the effective approaches to modified release to reduce daily administration frequency. In this study, a pulsatile release tablet of nicorandil was formulated by fumaric acid dry coating around the core tablet including nicorandil. The model tablets, which had different content ratios of excipients in the dry-coating layer, were characterized by a dissolution test. The results showed that the release lag time was generated with fast release profiles. Various lag time controls of tablets were achieved, from 60 to 310 min on average, by variation of outer layer composition. From an analysis of the relation between lag times and outer layer composition, the key ingredient for prolongation of lag time was found to be fumaric acid. To analyze the lag time generation mechanism, water penetration for tablet was measured. The results indicated that the penetration depth was proportionate to the square root of time and the lag time formation mechanism was simple water penetration through the matrix of fumaric acid to the tablet core. The results also showed that the Washburn equation could be used to design the lag time of the pulsatile release tablet in this study. In conclusion, novel release control technology using fumaric acid was appropriate to obtain a nicorandil pulsatile release tablet that has well regulated lag time.     

Use of indigenous microwave system for dissolution and treatment of waste from nuclear materials

Microwave heating technique has the unique advantages of low processing time, less consumption of reagents, homogeneous heating and maintenance-free adaptability to glove box. Dissolution of thorium and plutonium containing fuel viz sintered thorium oxide, thorium-uranium oxide and thorium-plutonium oxide pellets is one of the most difficult step for their analysis and characterization. Complete dissolution of the fuel samples is a pre-requisite for the analysis of fuel material in the solution form. Even a trace level of un-dissolved particle may interfere with the accurate and precise determination in the analysis. Large volumes of liquid and solid wastes are generated during the processing and analysis of samples. These wastes being radioactive can’t be disposed directly to sea or soil. They have to be segregated and categorised and all possibilities are explored to see the feasibility of retrieving the precious nuclear material. The present paper describes an overview of all the efforts made at AFFF for rapid dissolution of nuclear materials using an indigenous microwave digestion system as well as its use for the treatment of waste being generated.     

Reactions at the solid-liquid interface: surface-controlled dissolution of solid particles. The dissolution of potassium bicarbonate in dimethylformamide

We present a mathematical model for the surface-controlled dissolution of solid particles. This is applied to the dissolution of a solid having different particle size distribution functions: those of a monodispersed solid containing particles of all one size, a two-size-particle distribution, and a Gaussian distribution of the particle sizes. The dissolution of potassium bicarbonate in dimethylformamide is experimentally studied indirectly at elevated temperatures. We monitor the dissolution via the homogeneous deprotonation of 2-cyanophenol by dissolved KHCO3. The loss of 2-cyanophenol was detected electrochemically at a platinum microdisk electrode, and separately, the formation of the 2-cyanophenolate anion was monitored via UV-visible spectroscopic analysis. The results presented show that the kinetics of the loss of 2-cyanophenol behaves on one hand as a homogeneous chemical process and on the other hand as a dissolution-rate-controlled process. Initially, predissolved KHCO3 in solution deprotonates the 2-cyanophenol and homogeneous reaction dominates the observed kinetics, and at longer times, the observed kinetics is controlled by the rate of KHCO3 dissolution. Modeling of the experimental results for the surface-controlled dissolution of KHCO3 in dimethylformamide (DMF) yielded a mean value for the dissolution rate constant, k, at elevated temperatures; k was found to have a value of (1.1 +/- 0.3) x 10(-8) mol cm(-2) s(-1) at 100 degrees C, and the activation energy for the dissolution was 34.4 +/- 0.4 kJ mol(-1) over the temperature range 60-100 degrees C.     

A stopped-flow microdialysis sampling-flow injection system for automated multivessel high resolution drug dissolution testing

A simple and robust flow injection on-line microdialysis system for multivessel drug dissolution testing is described. Microdialysis probes were used for sampling from the dissolution media. A stopped-flow dialysis mode with a 50-s stopped-flow period followed by 10-s injection at a perfusion rate of 2.8 ml min(-1) for each probe was used to achieve high resolution of dissolution events using relatively simple equipment and operation. The precisions obtained for simultaneous monitoring of dissolution profiles for six tablets were all better than 0.9% (RSD n=80) and the overall sampling frequency of the system was 360 and 60 h(-1) for each test vessel. The dissolution profiles of isoniazid fast-release tablet from three sources were determined to demonstrate the performance of the system.     

Surface-enhanced Raman scattering-active silver nanostructures with two domains

Generally, a controllable and reproduced surface roughness for surface-enhanced Raman scattering (SERS) studies can be generated through control of the electrochemical oxidation–reduction cycles (ORC) procedure. In this work, we propose a new sonoelectrochemical approach to prepare SERS-active substrates with two domain-Ag nanostructures. The method is based on a strategy of deposition–dissolution cycles (DDCs) by using a cathodic overpotential and an anodic overpotential from open circuit potential (OCP) in turn under sonication. The prepared SERS-active substrate demonstrates large Raman scattering enhancement for adsorbed Rhodamine 6G (R6G) with an enhancement factor of 2.3 × 10⁸ and a limit of detection of 2 × 10⁻¹³ M. The improved SERS performances can be successfully explained from the viewpoints of electromagnetic (EM) and chemical (CHEM) enhancements.     

Micronization of tolbutamide using rapid expansion of supercritical solution with solid co-solvent (RESS-SC) process

Micronization of a sulfonylurea antidiabetic agent, tolbutamide, using rapid expansion of supercritical solution with solid co-solvent (RESS-SC) process was investigated in this study. Menthol was selected as the solid co-solvent in the RESS-SC process owing to its high vapor pressure and ease of removal by sublimation. The tolbutamide particles were micronized successfully from its original mean size of 89.4 ??m to the smallest mean size of 2.1 ??m through the RESS-SC process. The use of solid co-solvent in this process enhanced the saturated solubility of tolbutamide in supercritical carbon dioxide and inhibited the particle growth during pressure expansion after the nozzle. In addition, polymorph conversion from form I to form II after the RESS-SC process was confirmed by XRD and DSC analyses. Measurements of the dissolution rate profiles before and after the RESS-SC process were also investigated. It is shown that the micronized tolbutamide by the RESS-SC process had novelty in dissolution behavior compared to that of the original compound. Its dissolution rate was enhanced by 8.8 times after the RESS-SC process.     

Which is the determinant for cellulose degradation in cooperative ionic liquid pairs: dissolution or catalysis?

Catalytic conversion of sustainable cellulose to the value-added chemicals and high quality biofuel has been recognized as a perfect approach for the alleviation of the dependence on the non-renewable fossil resources. Previously, we successfully designed and explored novel and efficient cooperative ionic liquid pairs for this renewable material, which has advantages of high reactor efficiency than current technologies because of the dissolution and in situ catalytic decomposition mechanism. Here, the determinant of this process is further studied by the intensive investigation on the relationship between the cellulose conversion and the properties of ionic liquid catalyst and solvent. Scanning electron microscope (SEM), thermogravimetric analysis (TG) and elemental analysis were used for the comparative characterization of raw cellulose and the residues. The results demonstrate that this consecutive dissolution and in situ catalysis process is much more dependent on the dissolution capability of ionic liquid solvent, while comparatively, the effect of in situ acid catalysis is relatively insignificant.