Selective, stability-indicating assay of the major ipecacuanha alkaloids, emetine and cephaeline, in pharmaceutical preparations by high-performance liquid chromatography using spectrofluorimetric detection

A selective high-performance liquid chromatographic procedure has been developed for the determination of the major Ipecacuanha alkaloids, emetine and cephaeline, in a number of linctus and pastille preparations. The reversed-phase chromatographic procedure uses an octadecyl-bonded column with a mobile phase of aqueous methanol containing an ion-pairing reagent. A spectrofluorimetric detector is used for increased sensitivity and selectivity. Sample preparation is simple, involving either straight dilution for linctus formulations or simple dissolutions for pastilles. The procedure has been shown to be stability-indicating. Validation studies, to show that the method is precise, accurate and rectilinear, have been carried out on four linctus formulations and two pastille formulations. The method has been used to determine both emetine and cephaeline at levels as low as 5 micrograms/g in formulations.     

An algorithm for determination of the copolymer molecular weight distribution by Markov chain simulation

A simple and general algorithm, convenient for computer implementation, for calculation of the copolymer molecular weight distribution (MWD), its moments, copolymer composition, etc. from standard data has been developed describing copolymerization as a Markovian process. The algorithm is applicable for simulations of multimonomer copolymerization with monomolecular, bimolecular and mixed termination. It can be used for calculating the MWD of copolymers prepared under non-stationary conditions. Explicit formulae have been derived for the above parameters. They are exact even for low-molecular-weight oligomers. The calculation procedure involves nothing but plain matrix operations as matrix multiplication and inversion. For high-molecular-weight copolymers, even simpler dependencies that resemble those used for homopolymers can be used. A very simple numerical test has been proposed for checking their correctness.     

The use of stabilizers in the UV assay of ascorbic acid

Sodium thiosulphate (0.04%w/v) has been used to stabilize ascorbic acid in aqueous medium. The method has been used to assay ascorbic acid in commercial tablet preparations. It is very accurate, precise and reproducible. It compares favourably with official titrimetric method. The method is simple and can be adopted for the routine assay of ascorbic acid in single component tablet formulations.     

A simple and generalized model for predicting the density of ionic liquids

A simple and accurate model to predict the density of ionic liquids is presented. The proposed model is based on a generalized correlation that has been conveniently modified and experimental literature data have been used to fit the five model parameters, to finally propose an equation that allows predicting densities of any ionic liquid. The model uses the critical temperature, the critical volume, the normal boiling temperature and the molecular mass to estimate the density at temperatures commonly used in ionic liquid applications (270–360 K). A set of 602 density data for 146 ionic liquids has been used in the study. The results were compared with predictions of ten generalized corresponding states principle correlations available in the literature. These generalized correlations have not been applied to ionic liquids before so the appropriateness and accuracy of these models to ionic liquid density estimation are unknown until now. Results show that the new simple correlation gives low deviations and can be used with confidence in thermodynamic and engineering calculations.     

硅铝钡合金中铝量的快速测定

建立了硅铝钡合金中铝量的快速测定法，试样经酸溶解后，在一定条件下使铝与酒石酸钠的络合物被氟化钠破坏，定量地游离出碱，然后以酚酞作指示剂用硝酸标兴滴定碱，进而计算出铝量。     

Hard and soft acids and bases: structure and process

Under investigation is the structure and process that gives rise to hard-soft behavior in simple anionic atomic bases. That for simple atomic bases the chemical hardness is expected to be the only extrinsic component of acid-base strength, has been substantiated in the current study. A thermochemically based operational scale of chemical hardness was used to identify the structure within anionic atomic bases that is responsible for chemical hardness. The base's responding electrons have been identified as the structure, and the relaxation that occurs during charge transfer has been identified as the process giving rise to hard-soft behavior. This is in contrast the commonly accepted explanations that attribute hard-soft behavior to varying degrees of electrostatic and covalent contributions to the acid-base interaction. The ability of the atomic ion's responding electrons to cause hard-soft behavior has been assessed by examining the correlation of the estimated relaxation energies of the responding electrons with the operational chemical hardness. It has been demonstrated that the responding electrons are able to give rise to hard-soft behavior in simple anionic bases.     

三氯化钛存在下碘酸钾滴定法测定锡

提出了采用铝加铁混合还原剂还原,三氯化钛存在下碘酸钾滴定法测定锡的绝对测量方法,研究了三氯化钛抑制氧的作用效果及作用机理。应用于巴氏合金中锡含量的测定,方法简便、快速,结果准确可靠。     

Immobilized hepatic microsomes for the synthesis of glucuronides

A method has been developed for the direct immobilization of hepatic microsomes. The technique is simple and efficient. The immobilized microsomes retain biological activity and can be used to perform enzymatic reactions.     

Quantitative NIR Raman analysis in liquid mixtures

The capability to obtain quantitative information of a simple way from Raman spectra is a subject of considerable interest. In this work, this is demonstrated for mixtures of ethanol with water and rhodamine-6G (R-6G) with methanol, which were analyzed directly in glass vessel. The Raman intensities and a simple mathematical model have been used and applied for the analysis of liquid samples. It is starting point to generate a general expression, from the experimental spectra, as the sum of the particular expression for each pure compound allow us to obtain an expression for the mixtures which can be used for determining concentrations, from the Raman spectrum, of the mixture.     

Assay of sulphur compounds with 1-chlorobenzotriazole

A simple but accurate potentiometric method for the estimation of certain sulphur containing organic compounds has been developed, based on their oxidation with 1-chlorobenzotriazole. A back-titration procedure can also be used. The nature of oxidation in different media is discussed and the oxidation products have been identified.     

Coating of titanium implant materials with thin polymeric films for binding the signaling protein BMP2

A fast and simple approach for immobilization using copolymers as interlayers is reported. The synthesized copolymers form stable self-assembled layers on implant materials like, e.g., titanium in a simple coating/drying/washing sequence and have functional groups which can bind proteins from an aqueous solution. The copolymer films have been characterized via ellipsometry and contact angle measurements and were tested for biocompatibility. An immunoassay was used to determine the amount of BMP2 and demonstrated an approximately 10-fold increase as compared to previously used self-assembled monolayers. A BMP2-responsive cell line with luciferase detection was used to determine the biological activity of the bound signaling protein.     

Determination of atorvastatin in human plasma by magnetic solid-phase extraction combined with HPLC and application to a pharmacokinetic study

A simple and sensitive analytical procedure by solid-phase extraction method combined with high-performance liquid chromatography and using of graphene–magnetite nanomaterials as sorbent has been developed for the determination of atorvastatin in human plasma. A magnetic solid-phase extraction method as a simple, fast, and efficient extraction technique has been used for sample preparation. A solid nanocomposite material, graphene nanosheets decorated with magnetite nanoparticles, was used as a magnetic adsorbent and the adsorption process was optimized in this study. RP C18 column was used with mobile phase composed of acetonitrile–10?mM orthophosphoric acid by isocratic elution with the flow rate of 1?mL?min^?1. Fluorimetric detection was used by the excitation wavelength at 282?nm and the emission wavelength at 400?nm. It was found that the calibration curve was linear in the 30–150?ng?mL^?1. Limit of detection and limit of quantitation values were found to be 10 and 30?ng?mL^?1, respectively. The intra-day and inter-day relative standard deviation values were less than 5.27%. It has been concluded that the new developed method provides fast, simple, cost reduced, and sensitive assay for atorvastatin determination in human plasma. This method is also applied to a pharmacokinetic study.     

A kinetic study of pyrolytic pathways to benzocyclobutene

A simple gas flow reactor simulating flash vacuum pyrolysis conditions is described which yields appoximate rate values for monomolecular gas phase reactions and which has been used for a comparison and optimisation of pyrolytic elimination reactions leading to benzocyclobutene.     

Substoichiometric determination of tungsten by neutron activation analysis

A method for the substoichiometric determination of tungsten by thermal neutron activation analysis has been developed based on the selective extraction of the tungsten dithiol complex into amyl acetate. The method is simple, rapid and accurate. It has been used in the determination of tungsten in alloy steel, meteorites and biological standard kale.     

Use of precise absolute gas viscosity measurements to test the classical slip correction for capillary viscometers at 25°C and 1 atm

Precise gas viscosity measurements of Kestin and coworkers and a simple capillary viscometer have been used to test the classical slip correction at 25°C and one atmosphere pressure. The results indicate that for capillaries with diameters between 0.015 and 0.025 cm. this correction is two to three times smaller than normally used.     

Structure and bonding in proteins: Part 1. The electron organisation in the amide unit

A consistent set of numerical information on the electron organisation in the amide unit has been obtained for a number of small amides, using the readily available Gaussian-70 computer package and a modest amount of computer time. There is good agreement with experimental facts concerning bond lengths, bond angles, rotation barriers and cis/trans energy differences. The results have been analysed in terms of simple molecular orbital theory and other simple valence ideas to make the results intelligible in a physical sense, so that they may be used in larger molecules. The rotation barrier about the CN bond seems to be a simple π-electron conjugation effect, whose magnitude is influenced in the main by the internal geometry of the CNO fragment rather than by substituents.     

Interference by second order reactions in activation analysis

Equations to calculate the second order reaction interferences in activation analysis have been derived. A simple approximation as well as the exact solution have been investigated. A new algorithm is proposed for fast and accurate calculations, without the need of a computer with high precision arithmetic. The method can be used for all higher order reaction chains. Aspirant NFWO     

Novel conformationally locked inositols: from aromatics to annulated cyclitols

A new family of ring-annulated inositols with "locked" conformations has been designed to deliver a range of these biologically important entities in "unnatural conformations" while retaining their "natural configurations". The simple "tool" of trans ring fusion has been used to "lock" the conformation of the annulated inositols. Short, simple syntheses of a range of these novel cyclitols have been achieved from readily available aromatic precursors such as tetralin and indane. Along the way, annulated C(2)-symmetric cyclohexadiene-trans-diol (trans-CHD) derivatives have been prepared for the first time and serve as the pivotal building blocks for generating the oxy-functionalization pattern of inositols. The presence of chemo-differentiated hydroxyl groups in our novel inositols is expected to facilitate the installation of phosphate diversity to harness the biological potential of these entities.     

Microband electrodes fabricated by screen printing processes: Applications in electroanalysis

A novel method for the simple and cheap manufacture of microband and multiple microband electrodes is described. The construction technique is based entirely on the screen printing of the surface of alumina tiles with conducting and insulating ink materials. The range of potentials over which the electrodes may be used has been determined by basic electrochemical studies. These electrode systems have been used successfully for the measurement of vitamin C, vitamin B(1) and paracetamol, which illustrates, their potential as useful tools in the field of electroanalysis.