The applied field comprises {HEAD ~ a first, external magnetic gradient} which moves magnetically responsive particles to a region of {TAIL ~ a collection vessel} 
The applied field comprises { HEAD ~ a first , external magnetic gradient } which moves magnetically responsive particles to a region of { TAIL ~ a collection vessel }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL