Re: Swipe Testing

[Christian Schoenhofer <schoenho@via.at>]

Schoenhofer
Habichergasse 31/7
A-1160 Wien
AUSTRIA
Tel./Fax: +43-1-4955308
Mobiltel.: +43-664-3380333
e-mail: schoenho@via.at

----------
> Von: William Lorenzen <LORENZEN_W@A1.TCH.HARVARD.EDU>
> An: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Betreff: Swipe Testing
> Datum: Dienstag, 30. September 1997 16:17
> 
> What swipe test media are commonly used when the analytical method is
liquid 
> scintillation counting?  I am currently using "Whatman" Number 1 filter
papers 
> (42.5mm).
> 
> I know some use cotton swabs for instance...
> 
> Any of you who are conducting wipe tests care to share what you use and
do you 
> prep. them in any way (wet vs. dry)?
> 
> William A. Lorenzen
> Children's Hospital
> Boston, MA 02115
> 
> Phone:	617-355-7516
> Fax:	617-738-4526
> E-mail:	lorenzen_w@a1.tch.harvard.edu
> ----------------------------------------------------------------------

William and others interested in the topic:

The material we use depends on the circumstances and the surface from which
we take swipes. In cases where the surface to be tested is difficult to
access we use sticks with cotton at the end (sorry I do not know the
appropriate word in English - maybe it is cotton swabs?). We have used also
with success so called membrane filters (I think they are made from
cellulose nitrate.)  Depending on the radionuclide to be detected it may be
dry smears, for tritium or C-14 water moistened filters or cotton sticks
may be more appropriate and if the suspected contamination may be in
organic form also moistening with alcohol, aceton or similar may be
appropriate. This applies when the surface of a machine in a factory is
covered with oil.

Regarding liquid scintillation counting the membrane filters become
transparent on submersion into any cocktail. Glass fibre filters are
excellent because the scintillations are not quenched, but for very
low-level smears the K-40 in the glass fibre filters may be unwanted
because of much higher background. Cotton influences pulses only to a small
extent - practically little quenching. 

I would be very interested to hear more about the soluble material - could
anybody provide me with fax numbers or e-mail addresses of companies
selling this material?

Finally a strictly scientific question to Joel: What is the quench effect
of toalett paper, your shirt etc........?

Franz