title: Investigation of the glidant properties of compacted colloidal silicon dioxide by angle of repose and X-ray photoelectron spectroscopy.
abstract: The optimal flow-enhancing effect of a new compacted, hydrophilic colloidal silicon dioxide (AEROSIL 200 VV Pharma) on microcrystalline cellulose (Avicel PH 101) and pregelatinized starch (Starch 1500) was found to be 0.25% under gentle and 0.125% under strong mixing conditions, as measured by the angle of repose. The effect could be explained by X-ray photoelectron spectroscopy (XPS) investigations. The Si 2p signals of the silicon dioxide indicated that the coverage of the excipient surface with AEROSIL was greater for all mixtures produced under strong mixing conditions and corresponded to a higher degree of de-agglomeration of the AEROSIL aggregates. The more extensive surface coverage of Avicel PH 101 as compared to Starch 1500 could be explained by the particle morphology on the one hand and by the XPS C 1s signals on the other. Due to the different conformation of the two excipients, Avicel PH 101 offers a higher density of hydroxyl groups on its surface which are available for hydrogen bonding with the surface hydroxyl groups of hydrophilic colloidal silicon dioxide.
authors.affiliation: Department of Pharmaceutical Technology, Institute of Pharmacy, Eberhard-Karls-University, Tübingen, Germany.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Jonat
authors.forename: Peter
authors.initials: P
authors.lastname: Albers
authors.forename: Ann
authors.initials: A
authors.lastname: Gray
authors.forename: Peter C
authors.initials: PC
authors.lastname: Schmidt
mesh_terms: D002482:Cellulose / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D005079:Excipients / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013213:Starch / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003102:Colloids; D005079:Excipients; D012822:Silicon Dioxide; D002482:Cellulose; D013213:Starch; C109691:microcrystalline cellulose