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Shaun,

I don't know anything about using Drager tubes, 
but I seem to recall a study a while back 
(approx. 2000, maybe?) that ran into the same 
problem that you have.  They solved the problem 
by putting some silver phosphate into a cold 
finger on a vacuum extraction line, and then 
froze the gas sample into the cold finger and let 
the sample react for a few minutes at room T, 
presumably to form silver sulfide and phosphoric 
acid.  I recall reviewing the paper, and making 
sure that the authors included some additional 
details about this technique to clean up their 
gas samples (it wasn't a methods paper)

Unfortunately, I can't remember the authors, nor 
do I have a copy of the paper that I can find - 
maybe another Isogeochemer (who's younger and 
whose memory isn't shot like mine apparently is) 
might recall this paper?

Cheers,
Simon




>Dear all,
>
>We are trying to separate H2S from CO2 gas 
>samples in a vacuum line, prior to isotopic 
>analysis of carbonates which are variably mixed 
>with different proportions of different sulfide 
>minerals, particularly As-rich pyrite (which 
>seems to dissolve very readily in phosphoric 
>acid).
>
>I read with interest some of the discussion from 
>a few years ago on the Isogeochem list on this 
>topic, particularly with regard to the potential 
>use of Dräger tubes to remove H2S from CO2 
>samples.
>
>Does anyone have practical experience with 
>fitting and using Dräger tubes in a vacuum line 
>for this purpose?
>
>If so, could you tell me:
>
>(a) what model of tube you used (Drager 
>manufactures about 8 different tubes for H2S 
>detection)
>
>(b) What the OD of the tubes are, in order that 
>we can try to rig something to fit the tubes to 
>our existing 1/4" and 1/2" Ultratorr fittings.
>
>(c) What your "procedure" was to allow the tubes 
>to remove the H2S gas, i.e. did you trap water 
>before or after the Dräger tube, how long did 
>you allow the gas to interact with the Dräger 
>tube prior to capture of the CO2 for subsequent 
>analysis etc.
>
>Are there any other practical methods or 
>techniques that people have used? Ideally, we 
>are looking for a method that can readily be 
>used for hundreds of samples.
>
>Cheers,
>Shaun
>
>
>---------------------------------------------------------
>Shaun Barker
>Post-doctoral Fellow
>Mineral Deposit Research Unit
>Department of Earth and Ocean Sciences
>University of British Columbia
>Vancouver, BC   Canada    V6T 1Z4
>
>Tel: (+1) 604 822-1874
>fax: (+1) 604 822-6088
>
>email: <mailto:[log in to unmask]>[log in to unmask]
>----------------------------------------------------------


-- 
*****
Simon Poulson
Research Professor
Dept. of Geological Sciences & Engineering MS-172
University of Nevada - Reno
1664 N. Virginia St.
Reno, NV 89557-0138. USA
(775) 784-1104
Fax: (775) 784-1833
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http://www.mines.unr.edu/isotope/simonhome.html
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