PubMed · 6964527
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E Edorigo. [Amalgam phases: current views].. https://pubmed.ncbi.nlm.nih.gov/6964527/
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PURPOSE: The compression behaviour and the compactability of particles have been studied. In addition, an expression describing the bond strength over a tablet cross section was derived and these calculated values were compared with the experimentally determined tablet tensile strength values. METHODS: The compression behaviour of particles of a series of size fractions of four materials were assessed by tablet surface areas (particle fragmentation propensity) and by yield pressures (particle deformability), derived from in die Heckel profiles. The porosity and the tensile strength of the tablets were also determined. RESULTS: Sodium chloride and sodium bicarbonate possessed limited fragmentation while the converse applied for sucrose and lactose. Sodium chloride and sodium bicarbonate were the extreme materials with respect to particle deformability and compactability. Except for sodium chloride, a limited effect of original particle size on the compactability of the particles was observed. CONCLUSIONS: The observations on the compactability of the powders was explained by postulating that fragmentation affects mainly the number of bonds in a compact cross section, while deformation affects mainly the bonding force of these bonds, through a relationship with the contact area between a pair of particles. The deviations between the predicted strength of particle-particle bonds and the determined tensile strength values was explained by a high bonding capacity of some particles, e.g. due to an unpredicted high surface deformability, or by a fracture mechanic effect during tablet strength determination.
PURPOSE: This review describes a conceptual approach to the characterization of pharmaceutical solids. METHODS: Four flow charts are presented: (1) polymorphs, (2) hydrates, (3) desolvated solvates, and (4) amorphous forms. RESULTS: These flow charts (decision trees) are suggested as tools to develop information on pharmaceutical solids for both scientific and regulatory purposes. CONCLUSIONS: It is hoped that this review will lead to a more direct approach to the characterization of pharmaceutical solids and ultimately to faster approval of regulatory documents containing information on pharmaceutical solids.
The self-association of recombinant human interleukin-2 (rhIL-2) in solution was investigated as a function of pH and temperature using equilibrium sedimentation. Studies were performed at pH 3.6, 6.5 and 8.2, at 1 degree C and 20 degrees C. A model assuming an ideal single molecular species describes the data observed at pH 6.5 at both temperatures. At pH 8.2, the data from both temperatures can be better described by a weak monomer-dimer association equilibrium. The values of the association constants obtained indicate the presence of less than 10% dimer at a concentration of 1 mg/ml at both temperatures. At pH 3.6, aggregates with a Z average molecular weight of over 35 times that of monomeric rhIL-2 were formed. The smallest associating species present under these conditions corresponds to the monomer, which produces aggregates with a wide range of molecular weights. The monomer appears to be in equilibrium with the smallest aggregates, in that a model describing an indefinite association fits the data obtained at the highest centrifugal speed. No model was found to successfully describe the association of the monomer into the much larger aggregates observed at lower speeds. This may be the result of the lack of rapid thermodynamic reversibility of the larger aggregates. Temperature was found to have no significant effect on the largest aggregates that were formed at pH 3.6.