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  • 1
    Electronic Resource
    Electronic Resource
    Process-Induced Crystallinity Changes in Albuterol Sulfate and Its Effect on Powder Physical Stability (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 773-779 
    Details
    ISSN: 1573-904X
    Keywords: absorption ; albuterol sulfate ; amorphous ; crystallinity ; glass transition temperature ; moisture ; physical stability ; water vapor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pharmaceutical powders are often milled to achieve the optimum particle size. These size reduction processes can introduce dislocations and/or defects onto particle surfaces affecting the overall crystallinity of the powder. If enough energy is imparted, amorphous regions on the particle surfaces may be produced. These amorphous regions have the propensity to absorb significant quantities of water. In this study the effect of sorbed water on the physical characteristics of albuterol sulfate is investigated. Physical properties of this compound are studied in both micronized and unmicronized states using scanning electron microscopy, differential scanning calorimetry, powder x-ray diffraction, solution microcalorimetry, laser diffraction particle size analysis and water vapor sorption analysis. Subtle differences in crystallinity induced by air jet micronization are detected by several analytical methods. Amorphous to crystalline conversions are observed, the kinetics of which are found to be both temperature and relative humidity dependent. These experiments show the dynamic nature of micronized albuterol sulfate and aid in the determination of the actual physical state of this pharmaceutical powder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016232230638
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of the Twin Impinger for Size Measurement of Metered-Dose Inhaler Sprays (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1123-1127 
    Details
    ISSN: 1573-904X
    Keywords: impinger ; impactor ; calibration ; aerosol ; spray ; size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The calibration of the first stage of the twin-stage impinger, an instrument proposed for use in measuring the spray size from metered-dose inhalers, was performed with monodisperse aerosols by a standard technique for cascade impactors. The mean cut point was found to be not particularly sensitive to operating variables which may be expected to occur in practice. The cut point was close to that reported previously, although the collection efficiency curve was found to be slightly sharper. Calculations are reported on the expected results of measurements on aerosols in a two-stage instrument with an idealized perfect collection efficiency curve as well as the curve measured for the twin impinger. These results indicate that important characteristics of spray size distribution cannot be distinguished with an ideal two-stage instrument; the twin impinger is less capable than an ideal instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015835301929
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    Paper (German National Licenses)
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