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Toti:

I didn't weigh in on the "trapped bubble" issue earlier, but I will
now.  Our "prototype" MultiPrep was one of the first installed back
in 1996.  Even though GVI has made some modifications to the
orientation of the water trap and added a pump to assist in the
dispensing of acid, it has performed very well for nearly 38,000
dual-inlet carbonate analyses.  "Trapped bubbles" are a very rare
occurrence with our Wheaton vials.  I agree with earlier posters that
the phosphoric acid should have a slightly lower s.g. than the
classical value of 1.92, more like 1.88-1.89, to avoid bubbles and to
allow the acid to move through the silica capillary in a reasonably
short period of time.  This phenomenon also seems to occur more
frequently in those vials that have small tubules extending from the
bottom of the "V".

Concerning the shorter Wheaton vials and how they fit in the heated
rack, GVI years ago recommended using an additional aluminum plate, 4
mm thick, but of the same length and width as the heated rack, and
also drilled with 60 holes to match those of the rack, on top of the
rack.  The caps of the Wheaton vials rest on the upper surface of
this plate.  On top of this goes the lid.  Using this arrangement, we
have had no problems running carbonates and water samples by
dual-inlet.  Although we haven't done carbonates by continuous flow,
the MultiPrep needle does have to perform a similar multi-step
injection for dual-inlet water analyses as it does for carbonates by
continuous flow.

Steve


>Folks,
>
>Those very same vials (Wheaton V-shaped vial, part# 986284) are the ones I
>had problems with the elusive 'trapped bubbles'.
>
>Regarding their ability to fit in the 60 heated rack for the Multiflow
>(installed 2 years ago): one problem I did not expect was that the top of
>this aluminum block is cored out to accommodate Exetainer vials which are
>taller. So when the syringe pulls out of the septum after dropping acid it
>may (but not always) lift the  shorter Wheaton Vials up a little bit
>(~0.5cm). When the syringe re-visits the vial to sample the generated CO2
>it first stops on top of the septum to flush the inner needle and is then
>inserted all the way. If the vial is too high (that 0.5cm I was talking
>about), the syringe may partially inject during the flush cycle and I may
>loose some CO2. At this point I manually push the vials down after the acid
>injection, but thats not exactly an automated leave it for the weekend method.
>
>Toti.
>
>
>
>  At 12:45 PM 6/22/2005, Stephen S. Howe wrote:
>>Clemente and others:
>>
>>Wheaton makes a conical-shaped vial (they call them V-vials) that has
>>a volume of 1.0 mL, an O.D. of 13 mm, and uses a 13-425 screw cap
>>with a hole in the center that can be lined with silicone rubber
>>septa and Kel-F liners.  Wheaton's part number is 986284 and can be
>>found through Fisher, VWR, etc., or probably directly through
>>Wheaton.  You should make sure that the vials will fit in the holes
>>of the heated rack of the MultiPrep or MultiFlow attached to the
>>Gilson 222 XL autosampler before you buy a big batch of them.  The
>>heated rack that was installed with our MultiPrep in 1996 had holes
>>that could accomodate Wheaton vials that were actually being made
>>with an O.D. very slightly smaller than 13 mm at that time.  Shortly
>>thereafter Wheaton's vials "returned" to their nominal O.D. of 13 mm
>>and no longer fit in our rack.  Fortunately, we purchased quite a few
>>of the smaller-diameter vials but they are starting to wear out.  The
>>alternative would be to have the holes of our heated rack bored out
>>very slightly, and eventually, we may have to resort to this remedy.
>>
>>Hope this helps!
>>
>>Steve
>>
>>
>>--
>>---------------------------------------------------------------------------
>>Stephen S. Howe                         Office:  (518) 442-5053
>>Dept. of Earth & Atmos. Sciences        Stable Isotope Lab:  (518) 442-4471
>>Earth Science 352B                      FAX:  (518) 442-5825
>>University at Albany                    E-mail:  [log in to unmask]
>>1400 Washington Avenue        http://www.albany.edu/geosciences/sshowe.html
>>Albany, NY  12222-0001      http://www.albany.edu/geosciences/sirmslab.html
>>---------------------------------------------------------------------------
>
>Toti Larson Ph.D.
>Los Alamos National Laboratory
>Earth and Environmental Sciences                505.667.9894 (lab)
>Los Alamos, New Mexico 87545            550.667.8006 (office)