Evaluation of two concepts of crystallinity using calcium gluceptate as a model compound

Suryanarayanan, Raj; Mitchell, A.G.

doi:10.1016/0378-5173(85)90140-1

Cited by 58 publications

(26 citation statements)

References 22 publications

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“…18 In the 2-state model, there are distinct amorphous and crystalline regions as will be observed in physical mixtures of the amorphous and crystalline standards. On the other hand, the 1-state model does not assume distinct boundaries between the 2 phases.…”

Section: Degree Of Crystallinity Of the Dehydrated Phase-in Situ Quanmentioning

confidence: 99%

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Solid-vapor interactions: Influence of environmental conditions on the dehydration of carbamazepine dihydrate

2003

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KEYWORDS: carbamazepine, dehydration, water vapor, ethanol vapor The goal of this research was a phenomenological study of the effect of environmental factors on the dehydration behavior of carbamazepine dihydrate. Dehydration experiments were performed in an automated vapor sorption apparatus under a variety of conditions, and weight loss was monitored as a function of time. In addition to lattice water, carbamazepine dihydrate contained a significant amount of physically bound water. Based on the kinetics of water loss, it was possible to differentiate between the removal of physically bound water and the lattice water. The activation energy for the 2 processes was 44 and 88 kJ/mol, respectively. As expected, the dehydration rate of carbamazepine dihydrate decreased with an increase in water vapor pressure. While dehydration at 0% relative humidity (RH) resulted in an amorphous anhydrate, the crystallinity of the anhydrate increased as a function of the RH of dehydration. A method was developed for in situ crystallinity determination of the anhydrate formed. Dehydration in the presence of the ethanol vapor was a 2-step process, and the fraction dehydrated at each step was a function of the ethanol vapor pressure. We hypothesize the formation of an intermediate lower hydrate phase with unknown water stoichiometry. An increase in the ethanol vapor pressure first led to a decrease in the dehydration rate followed by an increase. In summary, the dehydration behavior of carbamazepine dihydrate was evaluated at different vapor pressures of water and ethanol. Using the water sorption apparatus, it was possible to (1) differentiate between the removal of physically bound and lattice water, and (2) develop a method for quantifying, in situ, the crystallinity of the product (anhydrate) phase.

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Section: Degree Of Crystallinity Of the Dehydrated Phase-in Situ Quanmentioning

confidence: 99%

“…18 In addition to the challenges in the selection of these standards, preparation of homogeneous mixtures is very difficult when the degree of crystallinity is very high (>90%) or very low (<10%). The proposed method does not require the generation of a standard curve.…”

Section: Degree Of Crystallinity Of the Dehydrated Phase-in Situ Quanmentioning

confidence: 99%

Solid-vapor interactions: Influence of environmental conditions on the dehydration of carbamazepine dihydrate

2003

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“…In a two phase model a mixture of amorphous and crystalline regions is assumed whereas in a one phase model a continuous transition with increasing lattice disorder from a fully crystalline to a 0% crystalline state is expected (23,24). If it is believed that the primary particles do not physically change, the only location of the amorphous content will be between these primary particles.…”

Section: Crystalline -Amorphous Absorbancementioning

confidence: 99%

Granule Characterization During Fluid Bed Drying by Development of a Near Infrared Method to Determine Water Content and Median Granule Size

Nieuwmeyer¹,

Damen²,

Gerich³

et al. 2007

Pharm Res

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Purpose. Water content and granule size are recognized as critical process and product quality parameters during drying. The purpose of this study was to enlighten the granule behavior during fluid bed drying by monitoring the major events i.e. changes in water content and granule size. Methods. NIR spectra collected during drying and water content of sampled granules were correlated by principal component analysis (PCA) and partial least squares regression (PLSR). NIR spectra of dried granules were correlated to median granule size in a second PCA and PLSR. Results. The NIR water model discriminates between various stages in fluid-bed drying. The water content can be continuously predicted with errors comparable to the reference method. The four PLS factors of the granule size model are related to primary particle size of lactose, median granule size exceeding primary particle size and amorphous content of granules. The small prediction errors enable size discrimination between fines and granules. Conclusion. For product quality reasons, discrimination between drying stages and end-point monitoring is highly important. Together with the possibilities to determine median granule size and to distinguish fines this approach provides a tool to design an optimal drying process.

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“…An increase in lattice disorder (decreasing crystallinity) usually results in an increase in volume and therefore a decrease in density. Changes in crystalinity should therefore be accompanied by gradual, progressive changes in density (127). The degree of …”

Section: Density Measurementsmentioning

confidence: 99%

Methods of amorphization and investigation of the amorphous state

Einfalt¹,

Planinšek²,

Hrovat³

2013

Acta Pharmaceutica

114

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.g., polymorphs) provides pharmaceutical scientists with an opportunity to select the preferred form of the material to be used in a formulation. This is very useful since critical properties, such as particle morphology and dissolution properties, are frequently different in the different physical forms of a material. The amorphous form of pharmacologically active materials has received considerable attention because, in theory, it represents the most energetic solid state of a material, and should thus provide the biggest advantages in terms of dissolution rate and bioavailability (1). However, the amorphous form also shows various disadvantages, such as lower physical stability compared to crystals.The structure of an amorphous solid is usually described as possessing a crystal--like short-range molecular arrangement, but lacking a long-range order. As illustrated by Fig. 1, the immediate environment of a molecule (m) in an amorphous solid may not differ significantly from that in a crystal (e.g., similar number of and distance to nearest neighbors), but an amorphous solid lacks any long-range transational-orientational symmetry that characterizes a crystal (1). However, this is only true when we are dealing The amorphous form of pharmaceutical materials represents the most energetic solid state of a material. It provides advantages in terms of dissolution rate and bioavailability. This review presents the methods of solid--state amorphization described in literature (supercooling of liquids, milling, lyophilization, spray drying, dehydration of crystalline hydrates), with the emphasis on milling. Furthermore, we describe how amorphous state of pharmaceuticals differ depending on the method of preparation and how these differences can be screened by a variety of spectroscopic (X-ray powder diffraction, solid state nuclear magnetic resonance, atomic pairwise distribution, infrared spectroscopy, terahertz spectroscopy) and calorimetry methods.

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Evaluation of two concepts of crystallinity using calcium gluceptate as a model compound

Cited by 58 publications

References 22 publications

Solid-vapor interactions: Influence of environmental conditions on the dehydration of carbamazepine dihydrate

Solid-vapor interactions: Influence of environmental conditions on the dehydration of carbamazepine dihydrate

Granule Characterization During Fluid Bed Drying by Development of a Near Infrared Method to Determine Water Content and Median Granule Size

Methods of amorphization and investigation of the amorphous state

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