Determination of the Surface Energy Distributions of Different Processed Lactose
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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- "An overview of the influence of particles size reduction over the surface properties of pharmaceutical ingredients by IGC. Pharmaceutical solid g d s Reference Acetaminophen " Trowbridge et al. (1998) Heng et al. (2006) Cefditoren pivoxil # Ohta and Buckton (2004) DL-propanolol hydrochloride " York et al. (1998) Felodipine " Chamarthy and Pinal (2008) Griseofulvine Chamarthy and Pinal (2008) " Feng et al. (2008) Otte and Carvajal (2011) # Otte et al. (2012) Ibipinabant " Gamble et al. (2012) Indomethacin " Planinsek et al. (2010) Lim et al. (2013) Lactose Ahfat et al. (2000) Feeley et al. (2002) Newell and Buckton (2004) " Thielmann et al. (2007) Shariare et al. (2011) Brum and Burnett (2011) Jones et al. (2012) Mannitol " Ho et al. (2012) Salbutamol sulfate " Ticehurst et al. (1994) Feeley et al. (1998) Salmeterol Xinofoate " Tong et al. (2001) (2006) Das et al. (2009) Sucrose Surana et al. (2003) " Hasegawa et al. (2009) Luner et al. (2012) Succinic acid " Luner et al. (2012) inhalation. Nowadays, dry powder inhalers (DPIs) are of great interest thanks to the absence of propellant and the stability of the formulation as a result of the dry state. "
ABSTRACT: Powders are complex systems and so pharmaceutical solids are not the exception. Nowadays, pharmaceutical ingredients must comply with well-defined draconian specifications imposing narrow particle size range, control on the mean particle size, crystalline structure, crystal habits aspect and surface properties of powders, among others. The different facets, physical forms, defects and/or impurities of the solid will alter its interaction properties. A powerful way of studying surface properties is based on the adsorption of an organic or water vapor on a powder. Inverse Gas Chromatography (IGC) appears as a useful method to characterize the surface properties of divided solids. The aim of this work is to study the sensitivity of IGC, in Henry's domain, in order to detect the impact of size and morphology in surface energy of two crystalline forms of an excipient, D-mannitol. Surface energy analyses using IGC have shown that the α form is the most energetically active form. To study size and shape influence on polymorphism, pure α and β mannitol samples were cryomilled (CM) and/or spray dried (SD). All forms showed an increase of the surface energy after treatment, with a higher influence for β samples (γs(d) of 40 mJ.m(-2) to 62 mJ.m(-2)) than for α mannitol samples (γs(d) of 75 mJ.m(-2) to 86 mJ.m(-2)). Surface heterogeneity analysis in Henry's domain showed a more heterogeneous β - CM sample (62 - 52 mJ.m(-2)). Moreover, despite its spherical shape and quite homogeneous size distribution, β - SD mannitol samples showed a slightly heterogeneous surface (57 - 52 mJ.m(-2)) also higher than the recrystallized β pure sample (∼ 40 mJ.m(-2)). Copyright © 2015. Published by Elsevier B.V.International Journal of Pharmaceutics 08/2015; 494(1). DOI:10.1016/j.ijpharm.2015.07.078 · 3.65 Impact Factor
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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  . To probe the whole surface, Thielmann et al. developed the method of IGC at finite concentration conditions . 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 . "
ABSTRACT: Methylene middle parameter [Formula: see text] , the product of the methylene group's cross-sectional area ( [Formula: see text] ) and the root square of its dispersive free energy ( [Formula: see text] ), is the key parameter to calculate the dispersive surface components of solids (γs(d)) using inverse gas chromatography (IGC) at different temperatures. The only method reported to calculate [Formula: see text] as a function of temperature is the Dorris-Gray method. However, the conventional values of [Formula: see text] calculated by the Dorris-Gray method depend heavily on theoretical aspects. This paper establishes a novel equation calculating the actual [Formula: see text] as a function of temperature using the latest and most accurate surface parameters of seven successive n-alkanes. The obtained actual [Formula: see text] values are slightly higher those of the conventional [Formula: see text] . At 20°C, the actual [Formula: see text] generates γs(d) values less than those generated using the conventional [Formula: see text] by ∼3%, and this reduction in calculated γs(d) values increases linearly to become ∼5% at 100°C. Therefore, using the new actual [Formula: see text] seems to mitigate the discrepancy between the γs(d) values measured by IGC and those measured by the contact angle method. Copyright © 2015 Elsevier B.V. All rights reserved.Journal of Chromatography A 07/2015; 1408. DOI:10.1016/j.chroma.2015.07.003 · 4.17 Impact Factor
- "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   . 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   . "
Article: Heterogeneity of carbon fibre[Show abstract] [Hide abstract]
ABSTRACT: A range of polyacrylonitrile (PAN) and pitch based carbon fibre types (high, standard and intermediate modulus fibres) have been characterised using both physical and chemical techniques, the results highlighting the heterogeneity of the fibre. Nano-indentation showed variation in stiffness between different fibres of the same type as well as variation along a 20 μm length of a single fibre. Tensile tests showed variance of approximately 25% in tenacity for three different carbon fibre types but less variability in modulus with values from 8% to 19%. Raman spectroscopy showed variation in the graphitic content both between fibres of different origin as well as variation, with 0.5 μm spatial resolution, along the length of a single fibre. Inverse gas chromatography surface energy measurements of larger samples of fibres were carried out using the novel approach of incremental surface coverage by varying the probe molecule concentration and revealed different levels of energetic heterogeneity for PAN based fibres collected at different stages of carbon fibre production. The heterogeneity of the unoxidised fibres (collected after carbonisation) was restricted to about 15% of the fibre surface whereas the surface oxidised fibre sample (collected after the electrolytic oxidation bath) was heterogeneous over more than 30% and the sized fibres were shown to be quite homogeneous.Carbon 03/2014; 68:240–249. DOI:10.1016/j.carbon.2013.10.084 · 6.20 Impact Factor