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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Pharmacy world & science 15 (1993), S. 105-115 
    ISSN: 1573-739X
    Schlagwort(e): Calcium phosphates ; Drug compounding ; Excipients ; Particle size ; Physics ; Powders ; Tablets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Ten commercially available calcium phosphates used for direct tableting were evaluated. The particle size distributions, powder properties, Sorption isotherms and pH values of aqueous slurries were compared. All samples showed good or at least sufficient flowability. Scanning electron micrographs illustrated the different kinds of manufacturing and gave hints on their expectable behaviour under compaction pressure. The sorption isotherms of identical chemical substances, which had been manufactured by different methods, differed strongly. This can be related to their specific surface areas. Most of the hydroxylapatites have large surface areas and can absorb up to more than 15% water at 93% relative humidity. Dibasic calcium phosphate dihydrate was non-hygroscopic and absorbed less than 1% water. With the exception of monobasic calcium phosphate monohydrate all calcium phosphates behaved quite neutral in water. Monobasic calcium phosphate monohydrate can be regarded as a solid acid. Although the calcium phosphates are usually stable substances, the role of crystal water in the case of dibasic calcium phosphate dihydrate and monobasic calcium phosphate monohydrate is problematic due to possible interactions with active ingredients.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Pharmacy world & science 15 (1993), S. 116-122 
    ISSN: 1573-739X
    Schlagwort(e): Calcium phosphates ; Drug compounding ; Ejection force ; Excipients ; Friability ; Hecket plots ; Lubrication ; Particle size ; Powders ; Tablets ; Tensile strength
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstracts Ten calcium phosphates suitable for direct compression (dibasic calcium phosphate dihydrate, dibasic calcium phosphate anhydrous and hydroxylapatite) were investigated with respect to their compressional behaviour. Except for Di-Cafos A all products gave tablets with sufficient to good mechanical strength. Nevertheless, there were differences between the products. All tablets prepared from the different products showed a high friability. This seems to be a problem of the calcium phosphates in general. On the other hand, the influence of magnesium stearate on the mechanical strength of the tablets was negligible for all products investigated. Moreover, a considerable effect of the particle size on the tensile strength of the tablets was found. The ejection forces and residual pressures were high in general, but critical only in the case of hydroxylapatites. Heckel plots were used to differentiate between plastic deformation and brittle fracture of the particles. In the case of calcium phosphates the slope of the Heckel plots indicated the hardness of the particles rather than their deformation behaviour.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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