Michel Preda

Polymorphic properties of micronized carbamazepine produced by RESS.

Carbamazepine microparticles were produced by the rapid expansion of supercritical carbon dioxide solutions (RESS) method. The characteristics of the resulting particles were studied by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and image analysis. X-ray diffractograms and SEM photomicrographs revealed that the crystalline nature of the produced carbamazepine microparticles depended on operating pressure and temperature conditions. Different polymorphs were obtained under various operating conditions. Under certain temperature (below 40 degrees C) and pressure (below 240 bar) conditions, it was possible to form primarily the carbamazepine polymorph stipulated by US Pharmacopeia. A significant reduction was observed in the particle size and size distribution range of carbamazepine produced by RESS. The processed particles had a mean diameter smaller than 3 microm and a size distribution range between 0.5 and 2.5 microm compared to unprocessed starting material with a mean diameter of approximately 85 microm and a size distribution range between 15 and 336 microm. Thus, this study demonstrates that the polymorphic characteristics of carbamazepine microparticles produced by the RESS method can be controlled by varying operating pressure and temperature parameters.

Structure–properties relationship in cross-linked high-amylose starch for use in controlled drug release

Cross-linked high-amylose starch (CLHAS), obtained by high-amylose starch cross-linking, was recently introduced as an excipient (Contramid) for monolithic dosage forms that are able to control drug release over 18-24 h. These control properties are related to tablet swelling and are strongly dependent on the degree of the cross-linking of CLHAS. The permeability of solutes through CLHAS hydrogels depends on the chemical structure of the polymer. The aim of this study was to obtain a better understanding of how modifications in CLHAS molecular structures at the level of long-range and short-range order during the cross-linking and processing conditions relate to the release properties of the CLHAS matrices. Structural parameters such as crystallinity contribute significantly to the physical and mechanical aspects of starch products. X-ray diffractometry, FTIR spectroscopy, dissolution tests in vitro, and mechanical hardness (of dry tablets) were found to be sensitive to the cross-linking degree (cld) variation. Best release properties and highest mechanical hardness were obtained from CLHAS matrices with low-to-moderate crystallinity, where the V- and the B-type structures coexist with amorphous regions. X-ray and FTIR profiles of dry CLHAS powders were found to be predictive for release properties of CLHAS tablets.

Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

Abstract The link between smectite composition in sediments from the northern North Atlantic and Labrador Sea, and deep circulation is being further investigated through detailed studies of the X-ray pattern of smectites and cation saturations. This allows clear distinction of dominant terrigenous sources associated to the main components of the modern Western Boundary Undercurrent. Time variations of smectite characteristics in two piston cores from the inlet and outlet of the Western Boundary Undercurrent gyre in the Labrador Sea indicate: (1) a more southern circulation of North East Atlantic Deep Water during the Late Glacial; (2) a step by step transition to the modern pattern of deep circulation during the Late Glacial/Holocene transition, with intensification of North East Atlantic Deep Water and Davis Strait Overflow; (3) an expansion of Davis Strait Overflow and Labrador Sea Water circulation in relation to ice surges and deposition of detrital layers; (4) an intensified circulation of North East Atlantic Deep Water during the Younger Dryas; and (5) a very recent increased influence of Denmark Strait Overflow Water beginning between 4.4 and

Physical and chemical characterization of a complexly contaminated scrubber dust — a by-product of copper smelting in Sachsen-Anhalt, Germany

Abstract A physical and chemical description of a scrubber dust slurry, known as Theisenschlamm, is presented. This material is generated as a by-product during extraction of copper from a mineralized Permian black shale (Kupferschiefer) in Sachsen-Anhalt, Germany. The Theisenschlamm consists of sulphide grains which are a complex solid solution of Pb, Zn, Cu and Fe. The crystal structures are modified forms of galena and sphalerite/wurtzite. Variations in the X-ray diffraction peak positions of these minerals reflect the poorly developed lattice structures of these phases. Anglesite is a secondary phase. The Theisenschlamm contains 18% Zn and 14% Pb as well as significant concentrations of PAH, PCDD and other organic compounds, rare metals and radionuclides (e.g. 210 Po and 210 Pb). The original particles have a median diameter of 1.25 μm, however, these particles are themselves aggregates of still smaller particles, typically of submicron size.

Trace element fluxes and natural potential risks from 210Pb-dated sediment cores in lacustrine environments at the Central Mexican Plateau

The accumulation, enrichment and provenance of selected trace metals (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, V and Zn) were studied in sediment cores collected from three lakes located in the Central Mexican Plateau, selected on the basis of their contrasting degree of urbanization: Santa Elena Lake, in a rural and remote area; El Tule Lake, in a rural and slightly urbanized area; and Chapala Lake, in a highly urbanized area. Grain size, magnetic susceptibility and sedimentary constituents such as organic carbon, calcium carbonate, as well as major (Al, Fe, Mn) and minor (Ca, Li, Rb, Sr, Th) elements were analyzed to explain the concentration trends of trace metals. Factor analysis (FA) was used to assess the provenance of the trace elements. The highest metal enrichment factor (EF) above natural concentration levels was found at Chapala Lake for Ag (EF = 3.9), although other trace element EF in all lakes was <2.0, indicating slight contamination. However, the concentration levels of Cr and Ni in all lakes, Hg and Zn in Chapala Lake, Cu in El Tule Lake and As in Santa Elena Lake were above international benchmarks for which adverse effects are expected to occur frequently, even for those metals only slightly enriched (e.g. As, Cr). Through FA, the terrigenous contribution was identified as the most important source of trace metals to the three lakes, most likely related to deforestation and erosion of the surrounding areas, followed by atmospheric transport of volcanic ashes, rather than to direct sources.

Oxidation treatment of a sulphide-bearing scrubber dust from the Mansfeld Region, Germany: Organic and inorganic phase changes and multi-element partition coefficients between liquid and solid phases

Abstract A low temperature oxidation process has been developed to separate Pb from Zn in a complexly contaminated scrubber dust. The material consists of approx. 50% galena (PbS) and sphalerite/wurtzite (ZnS), and also an amorphous component, a variety of different silicate and carbonate phases as well as naturally-occurring radionuclides and oil and grease. The two-stage process consists of a grinding stage followed by placing this material into a hydrogen peroxide solution. The resultant oxidation reaction is violently exothermic — the temperature rises spontaneously to approx. 96°C. The amount of solid phases remaining after completion of the reaction was reduced by approx. 40% and consisted largely of insoluble lead sulphate which retained the bulk of the radionuclides. Almost all of the zinc was placed into solution by this process as was the Cd, Re and Cu. The total PAH content of the original Theisenschlamm (468 ppm) was reduced to 11.25 ppm in the residual sediment and the PCDD/PCDF concentrations were reduced by approx. 40%. The radionuclides are almost totally concentrated in the solid phase. The method shows considerable promise as a separation technique for very fine-grained sulphide-bearing residues.

Surfactant separation as a technique for physical and chemical characterization of ore processing residues

When characterizing multi-phase materials, several authors have recommended separating the material into various fractions consisting of a reduced number of minerals. However, the common separation techniques are of limited value when treating ultra-fine-grained materials. We present in this paper a separation technique using tensio-active solutions which break up any particle agglomerates which may be present and facilitates sedimentation of component particles according to grain size. These fractions have a distinctive mineralogy and chemistry. The technique has been applied to two selected samples from two mining residue sites in Germany. Results from Bielatal, a tin residue, show that a large proportion of the arsenic and heavy metals are concentrated in a suspension fraction, which consists of clay minerals and amorphous iron oxyhydroxides. Silicates such as a micas and feldspar settle out quite rapidly, whereas, other minerals, such as hematite take longer. In the case of Dankritz, a uranium mine waste, the same technique was applied and similar results were obtained for the heavy metals distribution. Additional study indicated that radium is with barite and other radio-isotopes were associated with the fine suspension fraction.