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  • Author or Editor: Á. Erős x
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The interactions between surfactant and water were studied thermoanalytically focusing on the lyotropic liquid crystalline and microemulsion region in four ternary systems containing Cremophor EL and Cremophor RH40 as surfactants, neutral oil and isopropyl myristate as oily components. Subzero temperature DSC (SZT-DSC) measurements were carried out to determine the quantity of the bound water forming a hydration layer in surfactant microstructures, and the amount of free water, which has physico-chemical properties not much different from those of pure water. The variation of the surfactant:bound water ratio in the function of water concentration was also investigated. Phase changes detected by the SZT-DSC measurements were confirmed by polarization-microscopic and rheological investigations.

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Abstract  

A study was made of the possibilities of gradually decreasing the concentration of the toxic organic solvent in the process of microsphere preparation. Ammonio methacrylate copolymer-based microspheres were prepared by spray drying or conventional solvent evaporation techniques, and compared. The formulations were designed by varying the preparation methods and the concentrations of four polar cosolvents as independent variables. DSC was used to study the relationship between the changes in the independent variables and three of the main thermal events of the microspheres. Raman spectroscopy was used to investigate and confirm the possible interactions between drug and copolymer. Appropriate choice of the independent variables led to the molecularly dispersed drug in the polymer matrix. It was demonstrated that only the nature of the preparation method caused significant variations in the structure and thermal behaviour of the microspheres.

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Abstract  

Differential scanning calorimetry (DSC) was used in the investigation of the behaviour of coating free films. The films were produced from two film-forming polymers which are chemically different but equally used for producing controlled-release dosage forms: Eudragit NE 30 D (synthetically produced polymethacrylate copolymer) and LustreClear product (mixture containing natural and semi-synthetic components: microcrystalline cellulose, hydroxy-ethyl cellulose, carrageenan and polyethylene glycol). During their comparative analysis the characteristic parameters of the DSC curves obtained with dynamic measurement method were used and their changes as a function of storage conditions and storage time were observed. It was found that the thermoanalytical behaviour of the examined methacrylate-based Eudragit NE and cellulose-based LustreClear films was different. The specific enthalpy change of Eudragit NE fresh films was very little, but it increased considerably during storage. The specific enthalpy change of LustreClear films was much greater but its value shows only a slight further increase during storage. The results obtained help to choose the proper temperature for coating and drying.

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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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Abstract  

In pharmaceutical practice it is important and useful to know the crystallinity of materials and to monitor it during formulation development, production processes and storage. The purpose of this study was to assess the quantitative capability of DSC for determining crystallinity in crystalline/amorphous powder mixtures and to compare the accuracy of the DSC method with that of conventional powder X-ray diffraction. Alpha-lactose monohydrate was chosen as the model material. On the basis of this study it can be concluded, that DSC method can be applied safely for semiquantitative evaluation of the crystallinity of lactose samples consisting of an amorphous content higher than 20%.

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Journal of Thermal Analysis and Calorimetry
Authors:
Anita Kovács
,
I. Csóka
,
Magdolna Kónya
,
E. Csányi
,
A. Fehér
, and
I. Erős

The properties of the inner and the external aqueous phases, were studied in w/o/w multiple emulsions with light microscopic image analysis and differential scanning calorimetry (DSC). The importance of multiple emulsions lies in the presence of these aqueous phases, making them available for sustained, controlled drug delivery systems. Differentiation of these two aqueous phases, studying the effect of manufacturing technology on droplet structure, quantitative determination of phase volumes and any changes occurring during storage are essential when planning w/o/w emulsions. The present study uses microscopic observations combined with DSC measurements in order to identify the formed structure, at developmental stage in case of different components, preparation methods, and stirring rates. These tools are beneficial during manufacturing as in process controls, or to ensure product quality.

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Journal of Thermal Analysis and Calorimetry
Authors:
Á. Beretzky
,
P. Kása
,
K. Pintye-Hódi
,
J. Bajdik
,
P. Szabó-Révész
, and
I. Erős

Abstract  

The flowability of needle- or plate-shaped crystals is very poor and the direct compression of these crystals is difficult. Commercial phenylbutazone consists of needle crystals and it has three polymorphs.The aim of this work was to investigate the solid-state thermal stability of phenylbutazone at condition of the pelletization process (40°C; 60 min). The other aim was the preparation of phenylbutazone pellets with centrifugal granulator.Based non the flowability and the other parameters of, the pellets, they are suitable for capsule filling or tabletting. The centrifugal granulation and the conditions were favourable for the preparation of pellets from phenylbutazone in the form of needle crystals.

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Abstract  

The extents of the protective effects of coating films on the surface of crystals were determined. Three different samples were made with different quantities of coating fluid (Sepifilm LP 010 in 10% aqueous solution). Since the atomizing rate was constant, the coating time increased in parallel with the volume of coating fluid applied. The direct measurement of film thickness and smoothness is very difficult, and therefore indirect methods were used. Dimenhydrinate was chosen as model drug; this is a heat-sensitive antihistamine with a low melting point. This temperature can be reached during the tableting process. The behaviour of samples on exposure to heat was examined by differential scanning calorimetry. The water uptakes of the samples were determined with an Enslin apparatus. Plasticity was studied with an instrumented tablet machine. These indirect methods (thermal conductivity, water uptake and plasticity measurements) revealed connections between the results of the various experiments. An overlong coating time decreased the protective effect of the coating film.

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