Magnetic Beads

William of Occam occam at
Wed Dec 8 17:11:32 EST 1999

I wonder why nobody has introduced a small electromagnet for this purpose.
Should be cheaper than rare earth magnets.  Has anyone tried this?

Klaus Lehnert <k.lehnert at> wrote in message
news:82jt8n$9sq$1 at
> Stephen,
> the magnets in the commercial racks are rare earth magnets, which are much
> "stronger" (whatever the correct physical term) than normal magnets of the
> same size. I have used a normal magnet (U-shape, approx 20cm, size of foot
> ~1.5x3cm) with all sorts of magnetic beads. The big magnet works, but the
> only way to get the beads onto a small area is to put the small foot of
> big magnet directly under the tube and then collect the beads in the
> Washing seems less efficient that way, and they are much more difficult to
> resuspend. The commercial racks collect the beads in a circular area
> 3mm diam for eppendorf tubes) on the side of the tube, which makes washing
> and resuspension much easier. So, compared to the normal magnets, the
> commercial racks are much better.
> I am not sure whether they are worth their money, or if we are ripped of
> the biotech companies. To find out, one could try rare earth magnets from
> other sources. The "Lee Valley & Veritas" tool company (
> no affiliation, I only know because they are a woodworkers dream) sells
> small rare earth magnets for virtually nothing (from  $ 0.28 for a
> 0.22"x0.1" magnet; Order-No. 99K31.01), and their "strength/force" could
> increased if they are stacked like coins, "focussing" it into the small
> diameter area of the magnet's/coin's face. In fact, they claim they can't
> sell the 0.75" diameter model in numbers less than five because they are
> unable to separated them!) The only thing that has prevented me from
> them is that I don't want to pay $40 for shipment of a 50 cent magnet to
> Zealand (and the fact that I already have a commercial rack ;-))
> But hey, you're in the US of A, and they have bases in both the US and in
> Canada, so shipment would only be US$ 4.00.
> Maybe you can give them a try and let the rest of the world know.
> Cheers from down under
> Dr. Klaus Lehnert
> University of Auckland
> School of Medicine
> ----- Original Message -----
> From: Stephen Snowdy <snowds at>
> Newsgroups: bionet.molbio.methds-reagnts
> Sent: Wednesday, 8 December 1999 09:26
> Subject: Magnetic Beads
> > Does anyone know why the magnetic eppendorf holder costs so much?  It's
> > over 200 dollars (Pierce) for a rack to hold 6 tubes.  I'm not a
> > geologist so I must there any reason why one can't just use a
> > regular Radio Shack magnet?
> >
> > Thanx.
> >
> > Stephen Snowdy
> > UNC-Chapel Hill

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