A method for determination of particle magnetic susceptibility with analytical magnetapheresis

We recently developed a new method for simple determination of particle magnetic susceptibility using analytical magnetapheresis. This new method does not require laborious calibration plots and trial susceptibility values as do previous analytical magnetapheresis methods. The new method is based on balancing channel now rates and magnetically induced now rates for particle deposition in analytical magnetapheresis. The maximal now rate for complete particle deposition was determined experimentally and set to equal the magnetically induced now rate for determining particle magnetic susceptibility. This magnetic susceptibility determination generally takes less than 20 min. Several magnetically susceptible and ion-labeled particles were tested using this new method. The carrier magnetic susceptibilities were varied, and erbium ion-labeled particles were studied experimentally, resulting in successful susceptibility determinations of erbium ion-labeled particles and yeasts. The precision of each measurement was generally similar to 10%. Experimental determination of particle magnetic susceptibilities differed by less than 10% from reference measurements taken using a superconducting quantum interference device magnetometer. This method can determine minimal susceptibilities on the order of 10(-9) cgs. The minimum number of erbium labeling ions per particle required for complete deposition of silicas and yeasts was found to be 6.7 x 10(9). Analytical magnetapheresis shows good potential for use in simple determination of particle magnetic susceptibilities and should become a useful technique.