Quantification of Surface Amorphous Content Using Dispersive Surface Energy: the Concept of Effective Amorphous Surface Area |
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Authors: | Jeffrey Brum Daniel Burnett |
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Institution: | (1) Physical Properties, Particle Generation, Engineering and Control, Product Development, GlaxoSmithKline Pharmaceuticals, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, USA;(2) Surface Measurement Systems Ltd., Allentown, Pennsylvania, USA |
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Abstract: | We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective
amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized
square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline
and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems
are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and
crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples
is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for
bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle.
An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved
by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. |
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