contamination of centrifuges

["baumbaug@nosc.mil" <baumbaug@nosc.mil>]

        Radsafers ,


        One thing that I haven't seen brought up yet (regarding contaminated
centrifuges) is how the contamination of centrifuges may effect research
results!  In the past, when I worked at a university and inspected
laboratories, I would occasionally come across centrifuges/microfuges which
were contaminated with many 10s or 100s of thousands of CPM of removable
radioactive contamination.  

        What does this say for the accuracy/results of the researchers
experiments???  If they are spinning down a solution labeled with nanocuries
of a radioisotope and they are doing it in a microfuge contaminated with
more radioisotope than they have in their tube:

        a.      Are they contaminating their results with the
microfuge/centrifuge? - if not the tubes themselves (by some miracle) are
they contaminating their gloves and then the tubes (and then the inner vials)???

        b.      AND if they are contaminating their tubes etc., are they
doing it with the same radioisotope that they originally labeled their
product with?  Most researcher don't count by radioisotope on the LSC's,
they count using a wide-open channel...i.e. they count what's there and
don't ever think about "quantifying" their results.  NOTE: A small amount of
contamination with H-3 - while not a good thing - would probably not result
in as many spurious counts in a LSC as, perhaps P-32 would).

        Utilizing a heavily contaminated centrifuge/microfuge, what kind of
scientifically defendable results are they getting???  I've asked laboratory
researchers (the graduate student grunts that are not paid to think) and it
has never occurred to them that they may be skewing their data by
contaminating their experiments with contaminated laboratory equipment (I've
seen pipetters in use that were so heavily contaminated that they were
"many" mr/hr)  How many "results" are computated and published  - that are
really false positives??  

        I do know of one instance where cross contamination actually
happened resulting in an experiment having to be repeated.  A researcher was
labeling with H-3 and was perplexed that she was getting counts from her
bench area from a pancake probe when she was surveying the lab (they took
turns surveying - she only used H-3 but others in the lab used
P-32/I-125/I-131, S-35 and C-14).  Subsequent sleuthing revealed that much
of her experiment was contaminated with P-32 from (she concluded) a VERY
heavily contaminated microfuge.  Strict laboratory use guidelines were
drafted by the P.I. to make sure that this didn't happen again.

        Just my thoughts,


        Joel


..



>>hi,
>>
>>i'm new to radsaf and i would like to know if there are concerns/standard
>>practices with regards to the internal contamination of table centrifuges,
>>such as the eppendorf centrifuges.
>>
>>i perform swab tests for the lab and sometimes find readings over 10
>>000 cpm on a lsc especially for centrifuges used with p32 and s35. any
>>advice will be appreciated. thks!  
>>
>>
>>LEE T L William					
Joel T. Baumbaugh (baumbaug@nosc.mil)
Naval Research and Development (NRaD)
San Diego, CA., U.S.A.

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