Jaime,

We have been collecting waters from insects using an extraction line and did
notice a significant effect on H and O isotope ratios from the volatile
organics. We found that even a small amount of activated charcoal into the
collection tube you can completely remove the VOCs from the extracted water
and there is no fractionation associated with the charcoal. I'll send you
some data off the list to demonstrate this. Presumably the situation will be
similar with plant materials.

Anthony


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Anthony L. Michaud
W. M. Keck Foundation Laboratory for Environmental Biogeochemistry
School of Earth and Space Exploration
Arizona State University
Tempe, AZ 85287-1404
 
Web: http://kfleb.asu.edu
Tel: 480-727-8033
Fax: 480-965-8102
 
Mailing address:
 
Anthony Michaud
PSF-686
Arizona State University
Tempe, AZ 85287-1404
 
***Windsurf Everywhere***
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-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Jaime
Sent: Thursday, November 09, 2006 9:58 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] H-isotope Question

I am currently conducting experiments analyzing H-isotopes in water from 
various plant materials.  The water I have collected from the conifers 
is cloudy, so I am guessing that I also co-collected some small organic 
compounds.  My method for analysis is pyrolysis at a high temperature 
(1200-1400 degrees C).  I do not know how much of an effect the 
H-contribution from these compounds will be isotopically.  I have enough 
volume to split the samples, and am thinking about adding activated 
charcoal to half the sample and then filtering it before running (after 
West et al. 2006).  I am concerned about the potential for fractionation 
during this procedure.  Has anyone else run into this problem, or have 
other suggestions?  Thank you in advance.
Best,
Jaime L Toney