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Abstract  

The main purpose of our study was to produce microspheres containing diltiazem hydrochloride and to perform the thermoanalytical examination of the components and microspheres. Thermal analysis is a very frequently used method in the preformulation tests of solid dosage forms. Diltiazem hydrochloride is a calcium-channel blocker with short biological half life, so it is a potential candidate for sustained or controlled release dosage forms. Various techniques are available for the microencapsulation of drugs. The technique of spray-drying was used during our investigations. It was found that the crystalline form of the active agents could not be observed in the drug-loaded chitosan microspheres, which indicates the molecular dispersion of the drug in the matrix. It was established that the preparation conditions influenced the morphology and size of the particles. Moreover, the sphericity of the microspheres was good. On the basis of our investigations, the 1:1 diltiazem hydrochloride–chitosan ratio is suggested as the best ratio.

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Abstract  

Measurements of the masses of incorporated water and of the heats of hydration have been performed at 310 K, under air atmosphere saturated with water vapour, on three differently dehydrated samples of the Saccharomyces boulardii yeast in order to evaluate differences in physicochemical properties related to the following dehydration processes: cryodesiccation (or lyophilization) and thermodesiccation (spray drying and in-fluidized-bed heating).Thermogravimetric (TG) experiments have shown that the lyophilized yeast contains less residual water than heat-treated yeasts and that it incorporates more water and more rapidly. Isothermal water sorption of a spherical yeast cell has been represented by a two-parameter equation able to take account of a maximum of the hydration rate when this is taken as a function of time. On the other hand, isothermal DSC experiments have shown that hydration-heat values are higher for the heat-treated yeasts than for the lyophilized one. The TG and DSC results have been shown to be consistent with the idea that the physicochemical properties of a dehydrated yeast are related to cell-wall behaviour during desiccation.

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Abstract  

Mannitol and sorbitol are widely used in the pharmaceutical and food industry. There are some technological procedures such as spray-drying, freeze-drying, tablet compression, during which there is a possibility of heat effect. The purpose of this work was to study the thermal properties of sorbitol, mannitol and their mixtures. Furthermore, these materials and their tablet pressing were studied after melting and solidification. The results of the study prove that the use of sorbitol or mannitol alone is disadvantageous in melt technology. The use of mannitol is limited because of its high melting point (165C) and the polymorph transition after melting. Sorbitol (melting point: 96.8C) vitrifies from melt, therefore it is hard to handle during further processing. The melting point of the eutectic mixture (1.8% mannitol and 98.2% sorbitol) was 93.6C. This mixture was unsuited for pressing because of its glassy property. Our results showed that the most favourable composition was the mixture of 30% mannitol and 70% sorbitol (melting point: 131.8C) for tablet formulation. This mixture can be recommended for the formulation of such lozenge and hard candy tablets, where the active ingredient decomposes at higher temperature (>131.8C).

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Summary  

Solid dispersions were prepared to enhance the dissolution rate of rofecoxib. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used for the characterization of solid dispersions of polyvinyl pyrrolidone (PVP):talc:drug (3:1:1) and hydroxypropyl methylcellulose (HPMC):talc:drug (4:1:1). The DSC study indicated that PVP solid dispersion showed formation of fusion solution while HPMC solid dispersion showed no intermolecular fusion during the preparation of solid dispersions by spray dry process. The dissolution profiles and the calculated times for 75 and 90% drug release showed that dissolution rate of rofecoxib was improved in solid dispersions as compared to pure drug and physical mixtures. The DSC and XRD were successfully employed to find out the crystalline state of drug in the both solid dispersions. PVP solid dispersion gave better dissolution rate than HPMC solid dispersion. The drug was transformed from crystalline to amorphous form in PVP solid dispersion which was further conformed by XRD and DSC. The PVP:talc:drug solid dispersion can be used for the dissolution enhancement and thereby bioavailability of rofecoxib.

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For application in catalysis and adsorption processes, zeolites are synthesized on the surface of spray-dried kaolin microspheres. Various thermal effects are used for the rapid characterization of the zeolite type and content. From DTA measurements, the exothermic lattice break-down peak gives information on the zeolite type and the thermal stability of the sample. Measurements of the heats of immersion by a very simple and quick method allow conclusions about the type and the sorption properties of the zeolite part of the clay. The most precise method to estimate the zeolite content was a standardized technique of desorption and readsorption of water or organic compounds by means of a thermobalance.

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Abstract  

HPLC columns were packed with quasi-spherical montmorillonite particles which were prepared by spray-drying and then thermally treated. Separations of phenylureas (linuron, neburon, diuron and monuron), phosphothioate phenyl esters (parathion, methyl parathion and paraoxon) and other smaller substituted benzenes were performed on the columns. The relative retention of the substituted phenyl pesticides demonstrated the important role polar substituents play in the eluate-surface interactions and the strong influence of steric factors on these interactions. The retention of the pesticides decreased sharply as the polarity of the mobile phase increased. The retention of the smaller substituted benzenes showed a similar trend, but for these smaller molecules this trend was partially counteracted by the increased accessibility of interlayer spaces due to swelling as the polarity of the liquid phase increased. The role of the exchangeable cation (Na+, Co2+ and Cu2+) in the adsorption was found to be complex. The cations determine both the strength of interaction, which increases with the valence of the cation, and the accessibility of the interlayer adsorption sites which decreased with the valence.

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Introduction Milk is spray dried for easier storage, handling and transport. The spray drying process involves atomising the milk within a flow of hot air, where water is progressively evaporated from the droplets until dried

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, India. Lamivudine was kindly donated by Ranbaxy Limited, Paonta Sahib, Himachal Pradesh, India. Spray dried lactose (SDL) was kindly gifted from DMV Fonterra excipients, The Netherland. Magnesium stearate (MST), talc, and polyvinyl pyrrolidine K-30 (PVP

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Journal of Thermal Analysis and Calorimetry
Authors: Agna Hélia de Oliveira, Elisana Afonso de Moura, Márcia Ferraz Pinto, José Valdilânio Virgulino Procópio, Valmir Gomes de Souza, Fábio Santos de Souza, and Rui Oliveira Macêdo

. Thermal studies of pre-formulates of metronidazole obtained by spray drying technique . J Therm Anal Calorim . 2007 ; 89 : 775 – 781 . 10.1007/s10973-007-7874-5 . 18. Medeiros , AFD

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. Many food powders contain amorphous glassy components, such as amorphous sugars. Many spray-dried dairy powders contain lactose in its amorphous state. Amorphous components are thermodynamically unstable and there exists a driving force for them to

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