All

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.

Ian

_______________________________________________
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


Toti,

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
analyse.

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,

Karine

tlarson a écrit :

> Folks,
>
> 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
> this
> 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.
>
>
>
> 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)
>

--
*********************************************************

Karine CHARLIER
Departement de Geologie Oceanographie
UMR CNRS 5805 EPOC
Universite Bordeaux I
Avenue des Facultes
33400 TALENCE
FRANCE

Tel : 0 (33) 5 40 00 83 62
Fax : 0 (33) 5 56 84 08 48
E-mail : [log in to unmask]
Web : http://www.epoc.u-bordeaux.fr/

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