Thermal analysis of powdered alumina materials

How a DSC result is influenced by the particle size distribution of a powder sample is shown, and a simple and optimal method to be included in a routine DSC analysis (e.g., purity determination) to improve the reliability of the analysis is proposed. In case of-Al₂O₃ powder, most reliable heat capacity data can be obtained by preparing a powder with a self-similar particle size distribution with a distribution constant of 0.7, and by compressing it under a pressure of 1.5 MPa for a duration of 5 min or longer.This work is partially supported by the Research Fund of North Shore College of SONY Institute. R.O. wishes to express her gratitude to the support.     

Granulation of powdered materials in a high-speed granulator

Granulation of powdered materials in a drum-type high-speed granulator was studied. A mathematical model was constructed for describing the granulation in a high-speed granulator in which two processes, coagulation and disintegration, are combined. The constants of the integral transform core for coagulation and disintegration were determined from the experimental data obtained. The suggested mathematical model was shown to be adequate to the real process of granulation of a hydrophobic additive to asphalt concrete mix.     

Sum frequency generation studies of surfaces of high-surface-area powdered materials

We report the first observation of sum frequency generation (SFG) photons on high-surface-area powders, critically important materials in heterogeneous catalysis. We utilize SFG in total internal reflection (TIR) geometry and show that the TIR-SFG approach markedly reduces the destructive interference associated with nonlinear optical spectroscopy of small particle surfaces, making SFG studies of high-surface-area powders possible. The index of refraction of materials and their distance from the TIR-SFG prism are key parameters in generating and detecting the sum frequency signal. We find that TIR-SFG is highly sensitive to capillary condensation. To demonstrate the capability of the TIR-SFG technique, we measure the thermodynamics of methanol adsorption and desorption on high-surface-area SiO2.     

Computer-aided identification of compounds by comparison of mass spectra

A new identity-orientated search procedure for mass spectral libraries (IDS) was developed by extending the similarity search system SISCOM. The aim of IDS is an exact identification of pure compounds and mixtures on the basis of their mass spectra. The concepts and methods applied, e.g., filtering, feature selection and optimization with pattern recognition, are described. Chracteristics of IDS are summarized and demonstrated for several examples.     

Synthesis of Ag/ZnO mixture for powdered contact materials

The processes of a ultrafine Ag/ZnO mixture produced by coprecipitation from salt solutions were investigated. The coprecipitation in AgNO₃-ZnNO₃-Na₂CO₃ system was analyzed in the presence of surfactants, considering the pH value and a solution composition contribution. The optimal coprecipitation conditions were Na₂CO₃ precipitating agent excess of ～20%, providing a pH value of ～10, with subsequent thermal decomposition of the mixture at about 700 K. A thermal analysis of the precursor mixtures were carried out. The phase composition, dispersity and morphology of the precipitates were determined before and after a thermal treatment. The size decrease of the precipitated particles, as well as dispersity and distribution uniformity increase of the oxide inclusions in the target composite matrix is due to the presence of surfactants in solutions.     

Activated carbon and carbon-oxide composite materials derived from powdered cellulose

Activated carbons were prepared by high-temperature steam activation of carbonized samples of powdered cellulose and composite cellulose-inorganic materials based on it. The dependences of the yield of the material and in its physicochemical characteristics on the initial formula of the composite were found. The sorption activity of the carbons toward hydroquinone was determined, and the model reaction of hydrogen peroxide decomposition in their presence was performed.     

INAA and flame AAS of various vegetable reference materials

Summary INAA and flame AAS have been used for the analysis of a large number of vegetable reference materials. Out of all determined elements (28 by INAA and 11 by AAS) nine are common for both methods (Ca, Cd, Co, Cu, Fe, Mg, Mn, Na, Zn) and for these the possibilities of the two methods have been compared.     

Computer-aided quality assurance and certification of reference materials in the DANREF network

A network between 6 Danish laboratories with experience in quality assurance and quality control has been established with the aim of supporting the use and production of high-quality certified reference materials in Denmark. One of the tasks of the network was to develop a PC-program for computer-aided quality assurance and certification of reference materials produced by the network laboratories. This paper describes the design and features of the DANREF PC-program and shows examples of computer-aided evaluation of selected studies on reference materials. The program provides the network laboratories with the possibility to carry out harmonized statistical evaluation and documentation of homogeneity, stability and intercomparison studies in accordance with international guidelines and standards, e.g. ISO guide 35.     

Al-doped ZnO powdered materials: Al solubility limit and IR absorption properties

Al-doped ZnO powder was synthesized via the Pechini route with a doping rate varying from 1 to 4 mol.%. A solubility limit has been estimated under 0.3 mol.% of Al using X-ray diffraction refinements. The incorporation of aluminium into the ZnO lattice was investigated by ²⁷Al NMR, which suggests an extremely low amount of Al in a distribution of sites in ZnO. In order to assess the impact of such a low dopant amount, diffuse reflection experiments were performed for a wavelength range from 200 to 2500 nm. If the effect of doping was negligible for samples prepared at 850 °C, annealing at 1200 °C clearly reveals enhanced IR absorption properties for the doped samples, which are similar whatever be the nominal Al content.     

Computer-aided carbon-13 nuclear magnetic resonance spectroscopy for identification of terpenoid mixtures

The procedure for identifying triterpenes in mixtures is based on the simulation of ¹³C-NMR spectra for probable mixtures and comparison of these with a specialized spectral data bank. The system was designed to facilitate the analysis of complex mixtures of terpenoid compounds. A special matching procedure was developed and its efficiency is discussed. The method is demonstrated for a mixture of five triterpenes isolated from Vernonia cognata.     

Modern approaches to the production of carbon materials from vegetable biomass

Recent trends in methods for the preparation of porous carbon materials (PCM) from vegetable biomass by physical and chemical activation methods are analyzed. Data on the effect of activating agents and also other parameters on the textural characteristics of PCMs were classified. A new direction for the production of PCMs was discovered in the use of high-ash biomass.     

Renewable vegetable raw materials as a base for preparing versatile functional nanocomposites

A power-saving technology was developed for preparing functional nanocomposites from renewable vegetable raw materials and nanosized elements.     

Production of anode matrices from renewable vegetable raw materials, including agricultural waste

Carbon modifications (anode matrices) were produced from renewable vegetable raw materials, agricultural crop waste, by pyrolysis in a quartz reactor without access of oxygen at 900°C, as well as by mechanical synthesis, and their characteristics were examined.     

A multi-pumping flow system for chemiluminometric determination of ascorbic acid in powdered materials for preparation of fruit juices

A multi-pumping flow-based procedure with chemiluminescent detection is proposed for the determination of ascorbic acid, AA, in fruit juices (powdered form). The method relies on the inhibitory effect of AA on the oxidation of luminol by hydrogen peroxide in alkaline medium. The system comprises several discretely actuated solenoid pumps as the only active components. It handles 100 samples per hour, and requires 96 μl of sample, 42 μg of luminol and 105 μg of potassium hexacyanoferrate(III) per determination. The analytical curve is linear up to about 11 mmol l^− 1 AA, and detection limit is 0.17 mmol l^− 1 AA. The system yields precise measurements (r.s.d. < 1%; n = 11), and recovery ranges from 94% to 106%. Results are in agreement with the reference method (AOAC) at the 95% confidence level.     

The production of powdered candidate biological and environmental reference materials in the laboratories of the Joint Research Centre

The production of candidate biological and environmental reference materials in the laboratories of the Joint Research Centre, mainly on behalf of BCR, started in 1972 in Ispra and became concentrated in 1984 in Geel. Today, dedicated facilities for the transformation of biological and solid or liquid materials into dry powder samples are in use. The major guidelines followed in the conception of these facilities are described. Some typical examples of facilities developed or adapted to fulfil the specific requirements of professional CRM preparation are discussed, e.g. the whole-Teflon cryo-grinding equipment, the in-line controlled freeze-drier, the special facility for clean and dry handling of powders, the milling with classification equipment and the automation of bottling and labelling operations.     

Computer-aided prediction of QT-prolongation

Drug-induced cardiac arrhythmia is acknowledged as a serious obstacle in successful development of new drugs. Several methods for in silico prediction of acquired long QT syndrome (LQTS) caused by the pharmacological blockade of human hERG K+ channels are discussed in literature. We propose to use the computer program PASS, which estimates the probabilities of about 3000 biological activities, not only for prediction of hERG blockade and QT-prolongation but also for the analysis of indirect mechanisms of these actions. After addition in the PASS training set of 163 compounds with data on QT-Prolongation and re-training, it was shown that accuracy of prediction was 87.1% and 81.8% for hERG blockade and QT-prolongation, respectively. Using computer program PharmaExpert we found that in the predicted biological activity spectra there was a certain correlation between the hERG blockade and some other molecular mechanisms of action. Possible role of 1-phosphatidylinositol-4-phospate 5-kinase, dimethylargininase and progesterone 11 alpha-monooxygenase inhibition in hERG blockade was discussed.