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2011, №4

сс. 8-12

Articles

Key words: acetylization, supercritical fluids, cellulose, acetic anhydride, cellulose diacetate

Possibility  of cellulose acetylization by acetic anhydride in the supercritical carbon  dioxide (SC-CO2) medium in the absence of traditional catalysts,  toxic solvents and dilutants is demonstrated. As initial materials, three  samples of cellulose were tested: sulfite and sulfate celluloses and cellulose  obtained by low-temperature oxidative delignification in the SC-CO2  medium. Chemical composition of obtained cellulose diacetate is characterized.

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2011, №4

сс. 13-21

Articles

Key words: supercritical carbon dioxide, biomaterials, nano-scale hydroxyapatite, polylactide, selective laser sintering

Bioactive composites based on polylactide  powders and nano-sized hydroxyapatite (HAP) for the production of  three-dimensional scaffolds by selective laser sintering are manufactured using  supercritical carbon dioxide. A mixture of powdered polymers and nano-sized HAP  cannot be sintered directly by laser irradiation because continuous polymer  filaments cannot be formed due to the absence of permanent contacts between polymer  particles. This problem was resolved by employing for sintering composite  polymer particles already containing HAP nanoparticles fabricated in the  supercritical carbon dioxide medium. Mechanical tests and microscopy studies  demonstrate that HAP particles are uniformly distributed in the sintered  composites; the latter have no centers of destruction and withstand the same  mechanical loads as pure polymer. Produced structures can be used as scaffolds  in bone tissue engineering.

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2011, №4

сс. 22-50

Articles

Supercritical fluid chromatography and its application to analysis and production of high purity compounds

A.S. Samokhin, I.A. Revelsky, D.A. Chepelyansky, O.O. Parenago, O.I. Pokrovskiy, F.D. Lepeshkin, K.B. Ustinovich, A.I. Revelsky.

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Key words: supercritical fluid chromatography, pharmaceuticals, preparative SFC, SFC/MS

Principals  of supercritical fluid chromatography (SFC) and its application in various  fields are reviewed. SFC is compared to high-performance liquid chromatography  (HPLC). Fields of SFC application are considered. Special attention is paid to  the analysis of pharmaceuticals (and their impurities), biologically active  compounds and to the utilization of preparative SFC in the production of high  purity compounds. Different types of detection in SFC are discussed; special  attention is paid to the utilization of mass-spectrometric detectors in SFC.

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2011, №4

сс. 51-58

Articles

Key words: impurities in pharmaceuticals, generics, GC-MS, derivatization, supercritical fluid extraction, liquid extraction, atmospheric pressure photochemical ionization mass-spectrometry

The  possibility of comparison of original pharmaceuticals and their generics, based  on multidimensional profiles of impurities isolated from different samples by  supercritical fluid extraction and liquid extraction and registered by  gas-chromatography/mass-spectrometry with electron ionization (EI) and  atmospheric pressure photochemical ionization (APPCI) is investigated. The  utilization of the suggested approach allows one to increase of the number of  registered impurities and, thus, to identify the authenticity of  pharmaceutical samples and to compare the quality of original pharmaceuticals  and their generics.

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2011, №4

сс. 59-75

Articles

Conversion of brown coal in sub- and supercritical water at cyclic pressurization and depressurization

O.N. Fedyaeva, A.A. Vostrikov, A.V. Shishkin, M.Ya. Sokol, L.S. Borisova, V.A. Kashirtsev.

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Key words: supercritical water, brown coal, conversion, sulfur and oxygen removal

Conversion  of brown coal in sub- and supercritical water at 310÷460 °C and pressures up  to 30 MPa in the cyclic pressurization and depressurization modes is studied.  The temperature dependences of coal organic matter (COM) conversion, yield of  volatile and condensed products are obtained. Temperature dependence of  condensed substances yield has a maximum at 370 °C. At rising temperature the  fraction of high-molecular substances in condensed products is increased.  Cumulative conversion of COM into volatile and condensed products at heating to  460 °С was correspondingly  31.4 and 8.6 %. According to the data of  mass-spectrometric analysis of volatile products, elemental analysis of initial  coal, carbonaceous residue after conversion and condensed products, 82.3 % of  oxygen and 74.7 % of sulfur are removed from COM. The main products of  conversion of oxygen and sulfur containing groups are CO2 and H2S.

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2011, №4

сс. 76-87

Articles

Key words: supercritical drying equipment, polymer aerogel

A  detailed explanation of manufacturing of installation for supercritical drying  of polymer gels is presented. A special attention is paid to the preparation of  moisture-free carbon dioxide . The effectiveness of constructed equipment is  demonstrated on the examples of preparation of aerogel samples of given shape  from organic polymers of different chemical compositions.

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2011, №4

сс. 88-102

Articles

Supercritical fluid micronization of risperidone

V.N. Bagratashvili, A.M. Egorov, L.I. Krotova, A.V. Mironov, V.Ya. Panchenko, O.O. Parenago, V.K. Popov, I.A. Revelsky, P.S. Timashev, S.I. Tsypina.

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Key words: SCF micronization, risperidone, polymorphism

Comparative  studies of supercritical fluid micro nization processes of 50-100 mm size  risperidone pharmaceutical substrate using RESS and SAS approaches are  performed to enhance its bioavailability in human body. Both micronization  approaches allow obtaining risperidone microparticles of 5-20 mm size. SAS  approach, however, is more preferable for effective risperidone micronization,  since unlike RESS it doesn't cause any detectable contamination of risperidone  with organic co-solvent residuals (used in these processes) and also allows  obtaining risperidone microparticles of different shapes. It was revealed that  SAS micronization process causes a change of risperidone polymorphous form from  triclinic to monoclinic.

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