Drew, Bill and other friends of pyrolysis,

We got a tank of CO from Miesser through MG Industries (1-800-638-6360).
It is
designated Carbon Monoxide 4.7 (99.997%) ISOTOPE.  It has an isotopic
composition of -0.371 SMOW, very nice!  But we had to purchase the cylinder
and
MG puts CO in aluminium tanks.  Refills will not be as much as the first tank
we are told.

The previous research grade CO tank we got from Spectra Gases in NJ
(908-252-9300).  This gas ran well in the TCEA as opposed to some other US
tanks we tried - Why? there was a good discussion of the differences between
European and US CO last summer on this list server.  Marilyn Fogel has this
figured out I think.  We thought it was because of N2 contamination. Spectra
analyzed our CO and certified <0.05% N2 on that particular tank.  It was not
cheap, and has a O-18 value of -273 SMOW.  As expected we had a bit more
analytical variation than expected from the factory results with a machine gas
std that was this depleted.

We have had success running waters with the MG CO with a A200S liquid
sampler/auto-injector.  By using 0.5 ul syringes (carefully I might add) we
are
able to run water samples without dilution.  With dilution and a larger
syringe
we get 0.09 per mil reproducibility on fresh waters for O-18 and can calibrate
the dilution effect without having to go to solid samples.  For blood serum it
is about 0.15 per mil stdev., we have not run seawater yet, but then I quess
V-SMOW is seawater so it should not matter.  We analyze each sample 5 times
and
run a std near SMOW and two other depleted std's to correct for isotopic
non-linearity effects.

We are having some challenges with the solid samples.  It appears that our
AS200 autosampler has a large autosampler blank and a larger CO blank than the
AS128 autosampler.  Why?, we have not quite worked that out yet.  We even had
our small hole autosampler (AS200) rebuilt by Bruno.  It works well on the
NC2500 EA running N2 and CO2, but not on the Finnigan TCEA running CO. Of
course you don't need the large hole autosampler for the TCEA, the samples you
run are pretty small in folded silver boats.  It may have to do with the
higher
connector tube on the AS128, and the fact that the reactor is at 1450 degrees
instead of 1050 degrees on the NC2500 EA?  So those of you that are setting up
all these new TCEA's, don't use a AS200 autosampler and expect to get good
results - or if you do and get it to work call me collect and let me know how
you did it.

Sugars and organic compounds appear to run well in the TCEA and give good
yields, carbonates give poor yields and poor analytical results (sigh!) and
nitrates and phosphates give pretty good results if you pay close attention to
the blanks.  Depending upon what you run, the isotopic composition of the
blanks can change dramatically. Unfortunately ISODAT does not do blank
corrections well at all, so all corrections have to be done by hand offline
for
your data to make any sense.

I will give a talk and have a poster about these TCEA techniques and phosphate
O-18 results at the SF AGU annual Fall meeting in the phosphate special
session.  See you there.

Bill



At 04:24 PM 10/26/00 -0400, you wrote:
>
> Dear Drew and others,
>
> It appears we are all in the same boat, and some companies are trying to get
> European CO for us (MG Industries), but this taking some time.  We are also
> taking delivery of a TC/EA soon, and I have asked several times to the
> isotope community if anyone has any ideas about how to approach this
> problem.  Bill Showers is also a good person to contact.  Do not order any
> US-CO.  We did and made the $850-mistake, with a high purity tank and a
delta
> of about -350 per mil.  You are better off using your own internal standards
> than a ref. gas with such a negative value.
>
> -Bill
>
>
> --
> William Anderson
> Assistant Professor
> Earth Sciences Department and Southeast Environmental Research Center
> Florida International University
>
> Mailing address:
> Dept. of Earth Sciences, PC 344
> FIU
> 11200 S.W. 8th Street
> Miami, FL  33199
> USA
>
> office: 305 348 2693, sec. 348 3572
> SERC stable isotope lab:  305 348 3044
> fax: 305  348 3877
> email: [log in to unmask]



----------------------------------------------------------
William J. Showers
Dept. of Marine, Earth, & Atm Sciences
1125 Jordan Hall
North Carolina State University
Raleigh, NC  27695

(919) 515-7143 - voice
(919) 915-1498 - cell
(919) 515-7802 - fax
[log in to unmask] - office email

Even if you are on the right track, you'll get run over if you just
sit there.