Analysis of ferrofluids by capillary electrophoresis

A series of commercial and experimental water-based ferrofluids was analyze d by capillary electrophoresis (CE) coupled with diode array UV-visible det ection. The ferrofluids examined include a neutral dextran-iron oxide collo id, a cationic iron oxide colloid and four negatively charged ferrofluids. The effects of pH, ionic strength and applied voltage on the electropherogr ams were I-monitored. The electrophoretic mobility of the iron oxide partic les was calculated from the CE data and compared to the corresponding value s obtained from microelectrophoresis. Capillary electrophoresis provides a new, efficient and sensitive method to characterize ferrofluids in terms of surface charge, electrophoretic mobility and the level of purity. (C) 1999 Elsevier Science B.V. All rights reserved.