Dear Hans,
    Thanks for your email re platinum sticks. It is very useful to make contact with the manufacturer of the platinum sticks.
  We use platinum sticks placed in 5 ml vials with a septa on the top. The platinum stick is placed in the vial so that it is half in and half out of the water. We were told at one time that the equilibration took place at the water/gas interface but have also been told that it takes place in the vapor phase. When we tried to put the sticks entirely in the vapor phase, we had less success than when the sticks were half in and half out. Do you sell anything that keeps the sticks out of the water? We tried making stainless steel holders but these seemed to work poorly.
On a slightly different note, we also analyse plant and soil water that has been extracted using a distillation process with kerosene (aviation gas). There are small traces of solvent in the water and this also seems to contaminate the sticks or somehow cause problems with equilibration. For these samples we currently analyse by reducing the water to hydrogen over heated depleted uranium (works well but not an automated system). I'm hoping that by putting the sticks in the vapor phase, we can run these using the equibration method.
Looking forward to hearing from you.

From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Hans Friedrichsen
Sent: Wednesday, 16 January 2008 10:57 PM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] poisoning of D/H platinum rods/Hokko Beads by dissolved sulfide, and copper pre-treatment

to the water equilibration people,
just a reminder, the isotope equilibration between H20 and H2 happens in the vapor phase , so if there is no H2S in the vapor (depending on the pH of the liquid ) then there is no poisoning of the catalyst surface. But if you do have H2S in the vapor phase the catalyst will be inactive with time. And a second reminder: the equilibration occurs on the catalyst surface the catalyst has to be temperature controlled . some people place the catalyst well above the liquid phase at the top of a bottle where the temperature might be different by a few tenth of a centigrade compared to the temperaturecontrolled liquid and therefore they get different fractionation results. and a third thing: do not stop bacterial activity with HgCl2 this ruins the catalyst
Hans Friedrichsen
MS Analysentechnik (producer of the catalyst sticks)

-----Ursprüngliche Mitteilung-----
Von: Jonathan Wynn <[log in to unmask]>
An: [log in to unmask]
Verschickt: Di., 15. Jan. 2008, 19:15
Thema: [ISOGEOCHEM] poisoning of D/H platinum rods/Hokko Beads by dissolved sulfide, and copper pre-treatment

Hi All, 
I've read in the ISOGEOCHEM archives that the Platinum catalyst used in D/H analyses of H2O by equilibration can be "poisoned" by dissolved sulfides. Does anyone have experience to estimate a sulfide concentration above which this effect should be considered significant? I've also read about pre-treatment with copper to avoid this problem. Does anyone have a reference or advice for a standard pre-treatment? 
Jonathan Wynn 
Department of Geology 
University of South Florida 
4202 E Fowler Ave, SCA 528 
Tampa, FL 33620 
Tel. +1 (813) 974-9369 
Lab. +1 (813) 974-5278 
Fax. +1 (813) 974-2654 
[log in to unmask] 

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