Dear List Members

VG have recently completed the installation of an Isoprime MS with a
multiflow modular attachment for carbonate analysis in our University.

I have been provided with a recipe for the preparation of phosphoric
acid for carbonate analysis which involves the addition of phosphorous
pentoxide to the 85% phosphoric acid to remove water from the acid. This
will be achieved when the acid's specific gravity reaches 1.90. This
aspect of the acid preparation I was aware of from previous universities
I have worked at.

However, this new recipe I have also includes steps involving the
addition of Chromic-tri-oxide and hydrogen peroxide.

I would be interested to know if other labs use these two additional
steps in the acid preparation and what benefits they provide.

Cheers Steve

Dr Stephen Grimes
Lecturer in Stable Isotope Geochemistry and Climate Change
School of Earth, Ocean and Environmental Sciences
Room A422 Portland Square
University of Plymouth
Plymouth
Devon
Pl4 8AA
UK

Office. Room B513 Portland Square
Telephone. 01752 232457
Fax. 01752 232406
e-mail. [log in to unmask]
web page
http://www.plymouth.ac.uk/pages/dynamic.asp?page=staffdetails&id=sgrimes

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
Behalf Of Nathan B. English
Sent: 12 April 2004 17:04
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Running the carbonate fraction of phosphates
on a FM 252 with a Kiel Device

Dear Dr. Kohn,
         Thanks for your reply.  We're curious about the size and mass
of
the silver mesh you used, and how you inserted it into the stainless
steel
piping (i.e. did you just stuff it in there, or do you have some sort of
inline attachment)?  Oh, and what kind of machine do you use?  Thanks
again
for your time --- if it's really this simple then we're in good shape.

Best,
Nathan English

At 08:23 AM 4/12/04 -0400, you wrote:
>Hi,
>
>As you probably already know, the place to start for the analysis of
the
>carbonate component of phosphates is Paul Koch's article on preparation
>(Koch, P.L., N. Tuross, and M.L. Fogel, The effects of sample treatment
>and diagenesis on the isotopic integrity of carbonate in biogenic
>hydroxylapatite, Journal of Archaeological Science, 24, 417-429,
1997.).
>You'll find that different preparation processes yield slightly
different
>isotope compositions for the same material. That's worth keeping in
mind.
>
>As I understand the sulfur problem, the simplest solution is to react
it
>with silver to produce (solid) silver sulfide and O2, which can just be
>pumped away. I've heard two approaches for doing this. The first is to
use
>silver boats to load your samples. Presumably the sulfur reacts with
the
>silver before it makes it out of the acid. Since we don't use Ag boats,
>we've never tested that idea. Instead, we tried to solve the problem
>differently - by inserting some silver mesh into the SS tubing
downstream
>of the reaction. We've never seen any sulfur problems, even though
we've
>run hundreds of fossil phosphates, so we think it works.
>
>Matt
>
>
>>We are trying to figure out how to run the carbonate fraction of
phosphates
>>(from teeth) for d18O and d13C.  We have a Finnigan Mat (running on
Isodat)
>>hooked up to a Kiel device.  Has anyone tried or successfully analyze
d18O
>>and d13C of phosphates on their machines?  We are concerned that
sulfur in
>>the samples will alter the O and C results.
>>
>>To this end, we've considered removing the sulfur dioxide
cryogenically in
>>the first cold finger of the Kiel (T1 on Conf-C, Acon-C), but we are
unsure
>>of how to change the temperature parameter.  Any ideas?
>>
>>We would welcome any other suggestions on how to do this online (as
opposed
>>to running each sample by hand, ugh!).  Thank you in advance for your
time
>>and consideration.
>>
>>Cheers,
>>Nathan English
>>University of Arizona, Geosciences
>
>
>
>--
>
>
>********************************************
>Dr. Matthew J. Kohn, Assistant Professor
>Department of Geological Sciences
>701 Sumter St., Room EWS 617
>University of South Carolina
>Columbia, SC 29208
>phone: (803)-777-5565   fax:(803)-777-6610
>[log in to unmask]
>http://www.geol.sc.edu/kohn/index.htm
>********************************************