Article

Determination of the Surface Energy Distributions of Different Processed Lactose

Surface Measurement Systems UK, London, UK.
Drug Development and Industrial Pharmacy (Impact Factor: 2.1). 12/2007; 33(11):1240-53. DOI: 10.1080/03639040701378035
Source: PubMed

ABSTRACT Particulate interactions between drug and lactose carrier in dry powder inhaler formulations are affected by the heterogenous energy distribution on the surface of the individual compounds. A new method based on Inverse Gas Chromatography at finite concentration is applied to study the energy heterogeneity of untreated, milled, and recrystallized lactose of similar particle size distribution. Energy distributions for the dispersive surface energy and the specific free energy of ethanol are obtained. Milling causes an increase in surface energy due to formation of amorphous regions. Untreated and recrystallized materials have similar surface energies at low surface coverages but show clear differences in energy distribution.

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    • "The reason for this discrepancy is that IGC is usually used at infinite dilution conditions at which n-alkanes preferentially probe the higher energy sites on the solid surface [19] [20]. To probe the whole surface, Thielmann et al. developed the method of IGC at finite concentration conditions [21]. Then, Ho et al. compared the values of d s measured by IGC at finite concentration conditions with those measured by the contact angle method, and they found that IGC also generated higher values in the case of heterogeneous solid surfaces compared to the contact angle method, but similar values in the case of homogenous solid surfaces [22]. "
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    Journal of Chromatography A 07/2015; 1408. DOI:10.1016/j.chroma.2015.07.003 · 4.26 Impact Factor
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    • "This however results in the probe molecules preferentially interacting with the higher energy sites on the material surface, and interaction with lower energy sites is limited, if not excluded [18] [22] [23]. More advanced methodologies have been developed in the last decade, that allow the characterisation of the surface energy heterogeneity by using IGC under finite concentration conditions [22] [23] [24]. "
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    • "Applications of inverse gas chromatography (IGC) are wide ranging and include the monitoring of batch-to-batch variation (Gamble et al., 2010; Ticehurst et al., 1996), the impact of different processing routes (Thielmann et al., 2007), the detection of low levels of process induced disorder (Feeley et al., 1998), interactions of excipients and drug substances (Tay et al., 2010; Traini et al., 2008) and the impact of milling processes on the surface properties of materials (Balard et al., 2008; Chamarthy and Pinal, 2008; Gamble et al., 2012; Heng et al., 2006; York et al., 1998). However, applications of the approach to binary systems are almost as common and previously reported work has encompassed applications to investigate lubricated pharmaceutical systems (Swaminathan et al., 2006; Tay et al., 2010; Das and Stewart, 2012), surfactant systems (Bardavid et al., 2007), and dry coating or mechanofusion based coating of powders (Rousset et al., 2002; Kumon et al., 2006; Das et al., 2011). "
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