Liquid purification or separation – Processes – Using magnetic force
Patent
1992-06-02
1997-10-28
Savage, Matthew O.
Liquid purification or separation
Processes
Using magnetic force
210222, 356 36, 356417, B01D 3506
Patent
active
056814780
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and apparatus for separating superparamagnetic particles from a fluid suspension thereof and re-suspending them in the same or another fluid.
It has been proposed, e.g. in EP 106873, and U.S. Pat. No. 3,970,518, to use superparamagnetic particles for the immobilisation or isolation of a wide range of substrates. These may include proteins, nucleic acids, viruses and cells. Such particles have the advantage that they can be readily separated together with the immobilised substrate from a suspension thereof, for example a reaction medium, by application of a magnet to the wall of the vessel containing the suspension whereupon the particles are drawn to the wall as a relatively compact aggregate. The fluid is then readily removed from the vessel and replaced by a second fluid, for example a wash solution or a second reagent whereupon the magnetic field is removed and the aggregated magnetic particles re-suspended by relatively vigorous agitation. On the very small scale, the operator may effect such agitation by flicking the container with his finger but it will be appreciated that this will not be appropriate on the larger scale or in automated systems. It has been suggested that, rather than remove the magnet before re-suspension of the particles it might be possible to rotate the magnet around the container and thereby re-suspended the particles. However, it has been found that rotation of the magnet produces a rolling wave of particles; the particles staying as a compact aggregate but rolling over one another and thus continuing to entrap contaminants and reagents.
There is thus a need for a reliable and readily automated method of re-dispersing superparamagnetic particles after magnetic aggregation. It should be noted that superparamagnetic particles do not retain magnetisation as would be the case with magnetic particles. Thus, when the initial magnetic field is removed, there are no magnetic forces between the particles and the aggregate is held together by compaction.
We have found that by the first application of a magnetic field and, subsequently, a second application of a magnetic field, superparamagnetic particles may be aggregated and efficiently re-suspended without physical agitation. This finding is surprising in view of the fact that rotation of a magnet to change the magnetic field influencing the particle aggregate failed to produce effective re-suspension.
One aspect of our invention provides a method of separating superparamagnetic particles from a suspension thereof in a first fluid and re-suspending said particles in the same or another fluid whereby said suspension in a container is subjected to a first application of a magnetic field to draw said particles to a surface or zone of said container and subsequently said particles are re-suspended in the same or another fluid within said container by a second application of a magnetic field to draw the particles into said fluid.
The invention has the advantages that it leads to rapid and efficient re-suspension of the particles with little clumping and subjects the particles to relatively low shear. The method may be readily repeated several times so that the particles may be washed or treated with one or more reagents. In general, the particles will move across the chamber i.e., in a direction towards a central interior space of the chamber that is inwardly spaced from the peripheral interior surface of a container defining the chamber, at a speed related to the magnetic field and will thus comprise a moving suspension which contacts the fluid in the chamber particularly efficiently.
It will be clear to a person skilled in the art that the first and second applications of magnetic fields may be produced by the same magnet; the magnet being removed from close proximity to the container so that its magnetic field has little or no effect on the particles, and then being returned to the container at a different location such that it provides the second application of a magnetic field for re-suspension of the
REFERENCES:
patent: 2973096 (1961-02-01), Greaves
patent: 3219318 (1965-11-01), Hershler
patent: 3703958 (1972-11-01), Kolm
patent: 3970518 (1976-07-01), Giaever
patent: 3985649 (1976-10-01), Eddelman
patent: 4075462 (1978-02-01), Rowe
patent: 4297337 (1981-10-01), Mansfield et al.
patent: 4698302 (1987-10-01), Whitehead et al.
patent: 4895650 (1990-01-01), Wang
patent: 5147529 (1992-09-01), Lee et al.
patent: 5428451 (1995-06-01), Lea et al.
Lea Tor Erling
Naess Harald Kristian
Pedersen Bj.o slashed.rn Kirkaas
Diatec Instruments A/S
Savage Matthew O.
LandOfFree
Method and apparatus for magnetically separating and resuspendin does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for magnetically separating and resuspendin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for magnetically separating and resuspendin will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1023689