Re: Microfuge contamination

[paquette@shaman.nexagen.com (Tom Paquette)]

Contaminated microfuges are inevitable with common-use microfuges unless 
certain precautions are taken.  At the simplest level standard 1.5 ml 
"Eppendorf" tubes should not be filled beyond about two-thirds or they 
will leak during the spin.  However, flip-top tubes are difficult to 
handle and are almost guaranteed to produce splash-outs at some 
frequency with commonly used solutions like 70% ethanol. This makes a 
nasty mess during a procedure, with hot gloves, tubes, racks...  Flip 
tops are an archaic design, and screw-cap Eppe's with an O-ring are 
available. Some labs have adopted their use to reduce the incidence of 
contamination and leakage during radioactive centrifugations.  But, the 
best solution by far is to require that all microfuge centrifugation  
involving radioactive materials be done in the antiaerosol inserts 
available from Eppendorf via Brinkman Instruments and most of the big 
laboratory supply houses.  I do not know if these cups can be used in 
non-Eppendorf centrifuges.  Our experience is that these cups, even 
without their clumsy plastic snap caps confine virtually all leakages to 
the cup and the centrifuges are rarely contaminated.  Make your people 
use them. 
   With our shared common-use microfuges, we found that the centrifuges 
were a vector point for contamination, and that requiring the cups was a 
big step in lowering the frequency of little contamination incidents. 
There is also the phenomenon with common-use equipment, that people tend 
to believe that it was someone other that themselves who "did it".  The 
cups help clarify this and encourage some humility.  People rarely want 
a little rack of hot anti-aerosol cups on their own lab benches but will 
rarely go grab the survey meter to check the common centrifuge after a 
spin.  Make each user of the common centrifuge own a set of cups and 
confiscate the other adapters.  Even if a lab had the luxury of personal 
microfuges, the effort in cleaning the cups is much lower than cleaning 
the centrifuge and heads, and I would never personally attempt a 
radioactive spin without my antiaersol cups.
     By the way, the newer Eppendorf brand centrifuges generate enough 
higher G forces that this, along with 24-tube/12 AA-cup capacity, is 
enough to justify their purchase.  We had a machine shop make new 
aluminum covers for the heads in the older models.


-- 
Tom Paquette, PhD
Senior Scientist, RSO
NeXstar Pharmaceuticals
2860 Wilderness Place
Boulder, C0 80301
paquette@shaman.neXstar.com
biinsite@ix.netcom.com
303-546-7626
Fax 303-444-0672