Hi Lisa,

The exact reference eludes  me at the moment but Haiping Qi and Ty Coplen have recently published a paper with details about three wood (cellulose) standards.

Their delta values can be found on the web page of the USGS stable isotope lab at Reston.

http://isotopes.usgs.gov/lab/referencematerials.html

Best,

Wolfram

******************************************************
Prof. Dr W Meier-Augenstein, CChem, FRSC
Stable Isotope Forensics & Analytical Sciences

Robert Gordon University
School of Pharmacy and Life Sciences
The Ian Wood Building
Garthdee Road
Aberdeen
AB10 7GJ

E-mail:   [log in to unmask]

http://scholar.google.co.uk/citations?user=ty6c5IMAAAAJ
________________________________________
From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Lisa Welp <[log in to unmask]>
Sent: 26 October 2016 15:56:39
To: [log in to unmask]
Subject: [ISOGEOCHEM] tips for TCEA 18O analysis of cellulose

Hi,

I'm preparing to make 18O/16O measurements of cellulose and bulk organic
matter (leaves and wood).  I've searched the isogeochem archives and I
have a few questions for experienced members of the group.

1) Which reference materials?  From what I understand, it's hard to keep
cellulose dry and any water that it absorbs will change the 18O value.
That's why the IAEA doesn't assign values for their cellulose reference
material (only 13C values).  For that reason, many use benzoic acid or
water in silver tubes.  But neither of those materials are at all close
to behaving like cellulose in the combustion process.  So, seems like
there is no perfect answer here.  I'm leaning toward VSMOW and VSLAP in
silver tubes from USGS.  If so, what size (0.15 uL or 0.25 uL)?

2) Working standards?  I have some cellulose from Sigma.  I assume this
needs to be dried in a desiccator for a few days.  I also read that
granulated sugar from the grocery store could work.  Does this need to
be ground finely?

3) Sample + reference storage?  Is a desiccator OK?  Which kind? Glass
with phosphorous pentoxide or something less hazardous?  Or one of the
newer plastic vacuum kind?

4) CO working tank purifying scrubs?  Something to remove trace water
and organics, but I can't find this thread for details right now.

5) CO working tank isotopic composition?  How important is this? And how
do you predict what the approximate value will be when ordering?

6) Autosampler environmental control?  I suppose we could purge with He,
or heat and evacuate the carousel.  Pros/cons?

Thanks in advance.

Lisa

--
-----------------------------------------
Dr. Lisa Welp, Assistant Professor
Earth, Atmospheric, and Planetary Sciences
Purdue University
[log in to unmask]
http://www.eaps.purdue.edu/research/lwelp/

----------

This email has been scanned for spam and viruses by Proofpoint Essentials. Visit the following link to report this email as spam:
https://eu1.proofpointessentials.com/index01.php?mod_id=11&mod_option=logitem&mail_id=5yBV8BVejGGK&r_address=w.meier-augenstein%40rgu.ac.uk&report=1

________________________________

Robert Gordon University is the top university for graduate jobs in the UK HESA July 2015


Robert Gordon University, a Scottish charity registered under charity number SC 013781.

This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Please note that any views or opinions presented in this email are solely those of the author and do not necessarily represent those of Robert Gordon University. Thank you.