HI Ian--

We've been able to get the carbonates automated, at least for low temp
reactions (26oC).  We had to calibrate the acid dropping to 1/3 to 1/2 a
drop--basically not more than ~10 strokes per "drop", then pause the 0.4
or 0.5 sec.  Increase the number of "drops" in the method accordingly.
We also pump back atleast one full drop at the end--and have the
extraction needle insert on the opposite side of the septa, with the
intake facing away from the acid side.  Just be careful with Isodate
upgrades--make sure foward is still forward.

take care


ian cartwright wrote:

>We encountered different problems with acid delivery on our gas bench
>(mainly acid reacting with the septa and clogging the extraction needles)
>and went to a system where we introduced the acid into the exertainers in
>small cups that we then tipped following flushing. There was e-mail traffic
>on ISOGEOCHEM on this topic some time ago (including a description of the
>method) which should be in the archives. Other groups had come up with
>similar solutions. We have played around with various variations, and in the
>end sacrificed the elegence of doing the whole acidification-extraction
>process fully automated for a method that we have found to be robust.
>Dr Ian Cartwright
>Head - School of Geosciences
>Hydrogeology and Stable Isotopes
>Monash University
>Clayton Vic. 3800, Australia
>t: 03 9905-4887 / 4879, f: 03 9905-4903
>...water, our greatest resource
>-----Original Message-----
>From: Stable Isotope Geochemistry [mailto:[log in to unmask]]On
>Behalf Of Karine Charlier
>Sent: Tuesday, 21 June 2005 6:37 PM
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] Continuous Flow Carbonates
>We use a Multiprep on an Optima (dual inlet) here in Bordeaux and
>encountered the same problem of bubble on the bottom of our V-vials. As
>the acid didn't reach the sample, there was no reaction and no gas to
>It seems we had 2 problems at the time :
>- our H3PO4 was too viscous (1.92),
>- our vials were not cleaned very well, so the acid didn't spread out
>correctly on the glass.
>Now, we use H3PO4  with a density of maximum 1.90, we clean our vials
>with HNO3, and we don't have bubbles anymore...
>Good luck,
>tlarson a écrit :
>>I am trying to react carbonates using a GV Multiflow (Basically same Idea
>>as GasBench as far as I can tell in that the H3PO4 reaction occurs in a
>>helium environment and not a vacuum. So both camps are free to
>>answer), and
>>I noticed that after the H3PO4 was dispensed there was a tiny bubble
>>at the
>>bottom of my sample vial. This is obviously not a good thing. Has anyone
>>experienced similar issues with continuous flow carbonate analysis? Is
>>one advantage the running with a vacuum system such as the GV multiprep?
>>I am using 1ml Wheaton vials that have a cone-shaped bottom and the H3PO4
>>has a sg. of 1.94. What bottom-shaped vials are people using with the
>>GasBench or Multiflow? Maybe thats the problem. Reaction temp=90°C
>>Thanks in advance,
>>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)
>Departement de Geologie Oceanographie
>Universite Bordeaux I
>Avenue des Facultes
>33400 TALENCE
>Tel : 0 (33) 5 40 00 83 62
>Fax : 0 (33) 5 56 84 08 48
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