We have had a similar problem in our lab when flushing carbonate samples at
72ºC. In our case, we found that some of our septa that were over a year old
were having plugs removed when flushing. We ordered new caps and haven't had
any more problems with that. We think that the septa may deteriorate over
time.

Another problem that we have had is the caps coming loose after flushing and
causing leaks. After you flush at 40ºC, do you heat the vials to a higher
temperature? If so, the increase in pressure could cause the tops to loosen
just enough to cause a leak.

Currently, we are using Fisherbrand borosilicate vials and blue Labco caps
and we have not had any problems with leakage.

All the best,
Dana Biasatti


National High Magnetic Field Laboratory
Division of Isotope Geochemistry
Florida State University
1800 East Paul Dirac Drive
Tallahassee, FL 32310

e-mail: [log in to unmask]



-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]]On
Behalf Of Dave Mattey
Sent: Wednesday, September 07, 2005 7:01 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Leaking septa on Labco vials


We recently experienced a problem with leaking septa on labco vials using
our GV Multiflow system. It came to light  when some water samples returned
to us in pre-flushed vials had partially evaporated away.

The problem has been traced to the temperature at which the vials are
flushed - when the heater block is at 90°C there is no problem; I now
realise the batches of leaking vials were flushed at 40°C and the needle has
obviously (hindsight is a wonderful thing) punched a plug of rubber leaving
a pinhole in the septum, which is harder and less pliable at 40°C.

We mainly run carbonates and some DIC where the vials are flushed at 90°C
and have not had any problem apart from the two recent batches flushed at
the lower temperature. As we are about to start running 18O on water by CO2
equilibration where flushing will regularly take place at 40°C there is
obvious cause for concern here!

Has anyone else noticed this as a general problem?  I wonder if it could be
a local problem with the needle or with the batch of elastomer used to make
the Labco septa? Any input on this gratefully received.

Best wishes

Dave Mattey
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