Computer-aided identification of powdered vegetable materials

The use and limitations of the microcomputer as an aid for the analyst in the identification of powdered vegetable materials is presented and suggestions are given for extending the applicability of the method and the programs described.     

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.     

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.     

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.     

Radiotracer determination of dynamic parameters of a superphosphate granulator

An experiment on rabbits was carried out with the aim to check results obtained formerly with the help of the neutron activation analysis indicating that Na⁺ ions can be /by contrast to K⁺ ions/ only very slowly removed from the bone tissue by extraction with water. The data resulting from a radiotracer experiment with²²Na are in a good agreement with the above mentioned results.     

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.     

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.     

Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials

A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm.The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 μm) and particle size distribution in the range of 0.25-17 μm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS).The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials.The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation.     

Granulation of activated sludge in a laboratory upflow sludge blanket reactor

The creation of anoxic granulated biomass has been monitored in a laboratory USB (Upflow Sludge Blanket) reactor with the volume of 3.6 L. The objective of this research was to verify the possibilities of post-denitrification of residual NO₃-N concentrations in treated wastewater (denitrification of 10-20 mg L⁻¹ NO₃-N) and to determine the maximum hydraulic and mass loading of the granulated biomass reactor. G-phase from biodiesel production and methanol were both tested as external organic denitrification substrates. The ratio of the organic substrate COD to NO₃-N was 6. Only methanol was proven as a suitable organic substrate for this kind of reactor. However, the biomass adaptation to the substrate took over a week. The cultivation of anoxic granulated biomass was reached at hydraulic loading of over 0.35 m h⁻¹. The size of granules was smaller when compared with results found and described in literary reports (granules up to 1 mm); however, settling properties were excellent and denitrification was deemed suitable for the USB reactor. Sludge volume indexes of granules ranged from 35-50 mL g⁻¹ and settling rates reached 11 m h⁻¹. Maximum hydraulic and mass loadings in the USB reactor were 0.95 m3 m⁻² h⁻¹ and 6.6 kg m⁻³ d⁻¹. At higher loading levels, a wash-out of the biomass occurred. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Determination of the calibration cosntant gKs in the quantitative differential thermal analysis of powdered materials

In this article, results are presented for the determination of the calibration constant gK_s for the DTA of powdered materials related to the mass and particle size of the samples studied.It was established that gK_s represents a linear function of the coefficient of thermal conductivity of the samples studied. The determined value of gK_s is not valid for all experiments in quantitative studies of a particular system, but should be corrected depending on changes in the coefficient of thermal conductivity of the sample studied. These dependences are also valid for the DTA of metal systems, i.e. for cases in which the sample is in monolithic form.     

Isolation of carotenoids from plant materials and dietary supplements by high-speed counter-current chromatography

Methods for the isolation of lipophilic pigments from crude extracts of plant materials (spinach and sweet corn) by high-speed counter-current chromatography (HSCCC) were developed. Particular attention was given to (all-E)-lutein and (all-E)-zeaxanthin. However, the concomitant pigments neoxanthin, violaxanthin and beta-carotene as well as chlorophylls a and b were also considered. Furthermore, for the first time dietary supplements containing lutein and zeaxanthin were also used as a source for the recovery of carotenoids. Due to their simple matrix (oily excipient in soft gelatine capsules), sample preparation was facilitated and consumption of solvents was minimized. The carotenoids were characterized by 1H NMR spectroscopy, by LC/APcI-MS in the positive ionization mode, and by UV-vis spectroscopy.Data showed that the target compounds were of high purity (90 - 93%). Lutein and zeaxanthin may be used as reference substances for analytical purposes.     

Blend uniformity evaluation during continuous mixing in a twin screw granulator by in-line NIR using a moving F-test

This study focuses on the twin screw granulator of a continuous from-powder-to-tablet production line. Whereas powder dosing into the granulation unit is possible from a container of preblended material, a truly continuous process uses several feeders (each one dosing an individual ingredient) and relies on a continuous blending step prior to granulation.     

Nitride precipitation in a powdered iron alloy studied by thermoanalytical methods

Precipitation of nitrides (MnSiN₂, δ-VN_x) is studied in a powdered iron alloy (7.9 w/o Mn, 9.3 w/o Si, 1.2 w/o V, 0.03 ± 0.01 w/o N) of typical particle size 20 μm, by thermoanalytical techniques (TG, DTG, DTA). Equilibrium measurements are carried out at 900–1100°C in the N₂ pressure range 50–760 mm Hg. The nitride precipitates formed are isolated from the alloy matrix by a copper—ammonia separation method. The equilibration studies provide thermodynamic data which characterize the solubility of MnSiN₂(s) in the alloy used.     

Continuous introduction of powdered samples in emission spectroscopy The use of a tube-electrode

A device for the continuous introduction of powdered samples into spark and arc sources is described. The sample is pushed by a motor-driven spindle into the electrode gap through a tubular electrode. The method was found to be simple and versatile.     

Graphite hydrogenation in the presence of a mixture of powdered Ni and Zr

Strong promoting action of Zr in graphite hydrogenation in the presence of catalysts based on physical mixtures of powdered Ni and Zr has been established. The catalytic effect is ascribed to the extent of Zr surface oxidation.

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