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Optimizing Flow and Segregaton Properties of Lactose/Microcrystalline Cellulose Mixture for Tablet Compression.
Zámostný, P. ; Kreibichová, B. ; Hofmanová, D. ; Kulaviak, Lukáš ; Zelenková, K. ; Růžička, Marek
The present study deals with optimizing the flow and segregation properties of levocetirizine hydrochloride formulation, where the delay between homogenization and tablet compression was found to affect the tablet content uniformity. In addition to API, the base formulation comprised spray dried lactose monohydrate, milled lactose monohydrate 200 mesh, Avicel PH 101 microcrystalline cellulose, and minor excipients. Several alternative mixtures were prepared using the same total composition, but different grades of lactose and microcrystalline cellulose. These mixtures were then tested for the segregation behavior in an in-house segregation device and the flow properties using the Freeman FT4 powder rheometer. The segregation tests showed the grade of lactose is essential for mixture in-flow segregation. While SD lactose mixtures increased the API content in a direction countercurrent to flow, the milled lactose mixtures segregated API concurrently. Mixtures using both lactose grades showed combined effect, resulting in the least segregation due to the two segregation processes competing with each other. However, the segregation was extremely sensitive to ageing of the mixture. It was also found that each type of lactose causes a different flow regime of the mixture in process vessels. In order to improve the content uniformity of the tablets, it was found the volumetric flow regime of transport to tablet press is required as well as the aggregate formation should be prevented.\n
Plný tet: PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON CHEMICAL TECHNOLOGY -  PDF
Plný text: content.csg - PDF
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Vliv vybraných fyzikálně-chemických faktorů na mechanismus přepěňování piva
Poštulková, Michaela ; Novák, Pavel ; Vitoušová, K. ; Brányik, T. ; Růžička, Marek
Z výsledků, uvedených v tomto příspěvku vyplývá, že s rostoucím pH roztoku BSA o koncentraci 0,5 g/l roste intenzita jeho přepěňování. Rovněž bylo zjištěno, že zvýšení tlaku nad gushingovou matricí vedlo k úplnému potlačení přepěňování. Zařízení pro pozorování přepěňování se z praktického hlediska jeví jako vhodný nástroj pro predikci, stanovení a kvantifikaci přepěňovací aktivity a bude v budoucnu využíván pro další studium tohoto jevu.
Plný tet: SKMBT_C22013110513040 - PDF
Plný text: content.csg - PDF
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Rheology of Colloidal Dispersions: Deflocculation of Kaolin Dispersions
Guerreiro, M.I.A. ; Růžička, Marek ; Pěnkavová, Věra
All inorganic additives in their optimal concentrations proved to be effective at reducing the initial viscosity to 1%. In the case of NaOH two different trends were observed: firstly this additive behaved as a deflocculant agent where, at its optimal range of concentrations, the viscosity of kaolin dispersion reduced to its minimal value, secondly when used at concentrations above its optimal range, sodium hydroxide behaved like a flocculant agent increasing strongly the viscosity of kaolin dispersions. The possible cause was attributed to an excess of Na+ and OH- species in bulk media that promoted the reversible effect. Similar effect was also reported for NaCMC at high and medium molar weight, were the viscosity firstly decreased to a certain concentration of additive and then above that concentration started to increase. Thus low molar weight NaCMC was the most effective among the organic additives since it decreased the viscosity to 10% of initial viscosity. Qualitative evaluation showed that organic additives promoted more stable dispersions, in contrast to poor stability offered by the inorganic additives, with exception of NaOH that provided dispersions with good stability inside of its optimal range.
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