Colloidal Interactions Studied by Sedimentation Field-Flow Fractionation

• Published in: Journal of liquid chromatography & related technologies Vol. 20; no. 16-17; pp. 2525 - 2541
• Main Authors: Athanasopoulou, A., Karaiskakis, G., Travlos, A.
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 01.09.1997; Taylor & Francis
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Other chromatographic methods; Aggregation; Field flow fractionation; Barium Nitrates; Potassium Sulfates; Theoretical study; Potassium Nitrates; Hydroxyapatite; Kinetics; Polydispersed particle; Colloidal dispersion; Experimental study; Mobile phase
• DOI: 10.1080/10826079708005578
• ISSN: 1082-6076

Sedimentation Field-Flow Fractionation (SdFFF) is a relatively new technique for the separation and characterization of monodisperse or polydisperse colloidal materials and macromolecules. In the present work, with the aid of SdFFF, the interactions between the polydisperse, irregular Hydroxyapatite (HAP) particles were studied. The stability of HAP, which is of paramount importance in its applications, is dependent upon the total potential energy of interaction between the Hydroxyapatite particles. The latter, which is the sum of the attraction potential energy and that of repulsion, depends on particle size, the Hamaker constant, the surface potential, and the Debye-Hückel reciprocal distance, which is immediately related to the ionic strength of carrier solution. The larger the repulsion and the lower the attraction caused by increasing the particle's surface potential, and decreasing the effective Hamaker constant, or the ionic strength of the carrier solution, results in a higher stability. Variation of the ionic strength of the carrier solution by adding different amounts of electrolytes led to the size variation of HAP particles and to the determination of their critical aggregation concentration. From the variation of the number average particle diameter of HAP with time, for different salt concentrations, the rate constants for the bimolecular process of aggregation were determined. Comparison of the experimental rate constants found by SdFFF with those determined theoretically gives invaluable information about the aggregation mechanism.