Measurement of the surface energy of lubricated pharmaceutical powders by inverse gas chromatography

The objective of the study was to determine whether lubrication of pharmaceutical powders with magnesium stearate (MgSt) results in a change in the surface energy of the powder, and to assess whether surface energy changes, if any, are correlated to lubricant concentration and blend time. The surfac...

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Bibliographic Details
Published in:	International journal of pharmaceutics Vol. 312; no. 1; pp. 158 - 165
Main Authors:	Swaminathan, Vidya, Cobb, Jaclyn, Saracovan, Ilie
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 07-04-2006 Elsevier
Subjects:	Biological and medical sciences Cellulose - chemistry Chromatography, Gas Excipients - chemistry General pharmacology Inverse gas chromatography (IGC) Lactose - chemistry Lubrication Magnesium stearate Medical sciences Pharmaceutical technology. Pharmaceutical industry Pharmacology. Drug treatments Powders - chemistry Stearic Acids - chemistry Surface energy Surface Properties Magnesium stearate Inverse gas chromatography (IGC) Lubrication Surface energy Measurement Gas chromatography Pharmaceutical technology Stearate Magnesium Inorganic element Powder Quantitative analysis
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Summary:	The objective of the study was to determine whether lubrication of pharmaceutical powders with magnesium stearate (MgSt) results in a change in the surface energy of the powder, and to assess whether surface energy changes, if any, are correlated to lubricant concentration and blend time. The surface energies of microcrystalline cellulose (MCC), lactose, and blends of each material with MgSt, prepared at a range of concentrations and blending times were measured using inverse gas chromatography. The physical distribution of MgSt in the blend was mapped by energy dispersive spectrometry. Overall, there was a reduction in the dispersive surface energy of MCC–MgSt blends with increase in MgSt concentration, that was attributed to increasing coverage of the high-energy sites on microcrystalline cellulose by magnesium stearate. MgSt concentration had a larger effect on dispersive energy than the blending time of the powder with lubricant. X-ray maps of blend samples indicated a heterogeneous distribution of the lubricant in the blend and on the excipient particles. Measurement of the specific component of surface energy indicated that MgSt interacts with excipient powders through non-specific forces rather than acid–base interactions. No distinction among lactose–MgSt blends could be made on the basis of dispersive energy because of similar surface energies of the native materials.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0378-5173 1873-3476
DOI:	10.1016/j.ijpharm.2006.01.014