LSC problem solved!

["M. Woo" <m-woo@uiuc.edu>]

First of all, THANK YOU to everyone who responded to my original request
(28 in all, including responses directly to the list).

This long weekend my husband "treated" me to a long lecture about the
presence of free water in organic LSC fluid and how biological
contaminates can grow in it (he's a computer person now, but his PhD is
in biochemistry).  When I'd mentioned to him that our bottletop
dispenser was half-broken, i.e., it sucks air when drawing up fluid, he
said that it was drawing in outside air, which could result in water
condensation inside the bottle, resulting in free water.  He also
mentioned that a half-broken dispenser could draw back fluid into the
bottle if someone was using the dispenser incorrectly, i.e., touching
the tip to the fluid in the vial.  Either of the two scenarios could
result in contamination of the scint fluid.  He told me that biological
contamination of scint fluid is more common than I thought.

Rather STUPIDLY, although we'd tried two different bottles of scint
fluid from two different lot #s, they were already opened bottles.  One
was an old bottle where the fluid level had dropped below the level
which the dispenser could dispense and the other was the bottle in which
the dispenser is currently inserted.   Presumably contamination in the
old bottle was transferred with the dispenser to the next bottle.  A
brand new bottle of scint fluid (drawn with a pipette :) ) seems to have
solved the problem with the unexplained luminescence.  Our only defense
for not trying a brand new bottle initially is that the stuff is
expensive!  I am, however, considering a bout of self-flagellation for
not thinking of it sooner.  (just kidding)

My husband also "treated" me to the procedure for cleaning out the
bottletop dispenser, as he'd done it in the past.  I should *never*
bring my work home. :-/

Anyhow, all of you that said that the scint fluid was the cause - you
were right!  At least now I have a good reason to spend a few hundred on
a new dispenser.

Thanks again, everyone!

-- 
Melissa Woo, Health Physicist <mailto:m-woo@uiuc.edu>
Div. of Environmental Health & Safety
101 S. Gregory St., MC-225, Urbana, IL 61801
office	217.244-7233 fax 217.244.6594 <www.uiuc.edu/ph/www/m-woo/>
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