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Quantification of Surface Amorphous Content Using Dispersive Surface Energy: the Concept of Effective Amorphous Surface Area

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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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ACKNOWLEDGMENTS

The authors would like to thank Dr. Rachel Forcino, and Ms. Maria Barnett for supplying the samples of Drug Substance A, and amorphous lactose respectively. We also thank the reviewers for constructive comments.

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Authors and Affiliations

  1. Physical Properties, Particle Generation, Engineering and Control, Product Development, GlaxoSmithKline Pharmaceuticals, 1250 S. Collegeville Road, Collegeville, Pennsylvania, 19426, USA

    Jeffrey Brum

  2. Surface Measurement Systems Ltd., Allentown, Pennsylvania, USA

    Daniel Burnett

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  1. Jeffrey Brum
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  2. Daniel Burnett
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Correspondence to Jeffrey Brum.

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Brum, J., Burnett, D. Quantification of Surface Amorphous Content Using Dispersive Surface Energy: the Concept of Effective Amorphous Surface Area. AAPS PharmSciTech 12, 887–892 (2011). https://doi.org/10.1208/s12249-011-9655-5

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  • DOI: https://doi.org/10.1208/s12249-011-9655-5

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