Hi Berndt!

Like Simon, I use the Wheaton glass vials for carbonate digestion with
phosphoric acid, but we also use the same vials for oxygen isotopic analysis
of water samples after equilibration with CO2, in our MultiPrep, here at
Albany.  The vials are quite sturdy, if treated properly, and we have lost
relatively few over the past 6 years.  The one problem we have had, however,
is related to our having one of the first MultiPrep's produced.  The holes in
the heated aluminum block were drilled so that there would be a tight fit
with the vials to insure that the vials would reach the temperature of the
heated block quickly.  At the time our MultiPrep was made, Wheaton had some
manufacturing tolerance problems, and was producing the vials with a diameter
of about 12 mm, so that's the diameter of the holes in our block.  Not long
after, Wheaton correcting their manufacturing problems and began producing
vials with diameters closer to their stated diameter of 13 mm.  Consequently,
their newer vials do not fit in our rack.  I have tried a number of batches
of vials ordered over several years, but they are all too large in diameter
for our rack.  Fortunately, we purchased a large number of vials initially,
and a second MultiPrep rack, so in the future, we may have to have our
machine shop drill out the holes to accomodate the slightly wider diameter
vials.

Concerning septa and liners, as I have mentioned several times in the past on
Isogeochem, we use the 7/16" diameter pre-punched blue rubber septa from
Alltech, with a 7/16" diameter Kel-F liner between the septa and the top of
the glass vial.  The Kel-F is punched from a 0.010" thick sheet using an
Alltech 7/16" punch.  The sheets of Kel-F are from AIN Plastics.  Although we
have to punch the liners ourselves, it is far cheaper than buying pre-punched
Kel-F liners from the mass spec manufacturers.  For several years we used
pre-punched PTFE liners from Fisher but found that not only do we have many
fewer leaks using the Kel-F liners for carbonates, but that for water
samples, unlike the PTFE liners, the Kel-F liners did not adsorb CO2 during
equilibration, avoiding fractionations of 0.1-0.3 per mil.

Check the Isogeochem archives for details about the blue rubber septa and
punch from Alltech, and the Kel-F from AIN Plastics.

Steve


>>I know Labco Ltd. But they have no vials with a conical insert at the
>>bottom. I need this for small amount carbonat samples.
>
>
> Hi Bernd,
>
> Sorry, I didn't realise you were looking for vials for carbonates
> rather than waters.  The vials I've been using for carbonates with the
> conical inside are from Wheaton (http://www.wheatonsci.com/),
> catalogue #986284.  As for septa, there's a good selection of septa
> available from Supelco (via the www.sigma-aldrich.com web site).
> However, I'm not sure where to get PCTFE discs - but maybe
> teflon-faced septa (available from Supelco) would do the trick?  (I
> haven't had chance to try these yet)
>
> Cheers,
> Simon
>
>
> --
> *****
> Simon Poulson
> Dept. of Geological Sciences MS-172
> 1664 N. Virginia St.
> University of Nevada - Reno
> Reno, NV 89557-0138. USA
> (775) 784-1104
> Fax: (775) 784-1833
> [log in to unmask]
> *****