Analytical magnetapheresis is a technique for analyzing magnetic parti
cles in suspension. The magnetically susceptible particles form a depo
sition pattern from the suspending medium under carefully controlled f
low and magnetic field conditions. This technique was used to determin
e the effective magnetic volumetric susceptibility, Delta(chi), of hum
an lymphocytes labeled with an iron-rich protein, ferritin. Dynabeads
M450, monodisperse polymeric beads doped with magnetite, of a diameter
4.5 mu m, close to that of human lymphocytes, were used as a referenc
e. The experiment showed an almost complete deposition of ferritin-lab
eled lymphocytes at an average now velocity of 0.28 mm/s, a representa
tive magnetic held of 1.67 T, and a magnetic field gradient of 2.57 T/
mm. The calculated Delta(chi) (2.92 +/- 0.24) x 10(-6)[SI] (ferritin-l
abeled lymphocytes), and the corresponding number of ferritin molecule
s per lymphocyte was (1.75 +/- 0.44) x 10(7). In comparison, an almost
complete deposition of the Dynabeads was observed at a much higher av
erage now velocity, 15 mm/s, a much lower field, 0.164 T, and a much l
ower field gradient, 0.025 T/mm. These results corresponded to a much
higher Delta(chi) = 0.245[SI] (Dynabeads M450). These results offer im
portant guidelines in evaluating the use of ferritin as a soluble magn
etic cell label.