Particle magnetic susceptibility determination using analytical split-flow thin fractionation

Magnetic split-flow thin (SPLITT) fractionation is a newly developed SPLITT fractionation subtechnique for separating magnetically susceptible particles. Here, we describe determination of particle magnetic susceptibilities using a novel method, analytical magnetic SPLITT fractionation. This method is based on particle retrieval calculation under known flow-rates and magnetic field strengths. The flow axis of separation channel was oriented parallel to gravity to exclude gravitational effects on separation. Various carrier magnetic susceptibilities, magnet interpolar gap widths, and ion-labeled particles were studied experimentally, resulting in successful determination of magnetic susceptibilities for magnetically susceptible particles and various ion-labeled particles. The minimum level of particle magnetic susceptibility (chi) that could be determined in this study was about 5.0(.)10(-7) (cgs). The minimum number of erbium labeling ions per particle required for silica susceptibility determination was found to be 1.57(.)10(10). These determined values were consistent with relative standard deviations within 8% variation and within 9% of standard reference measurements using a superconducting quantum interference device magnometer. Analytical magnetic SPLITT fractionation shows good potential for use in simple determination of particle magnetic susceptibilities. (C) 2001 Elsevier Science B.V. All rights reserved.