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