Alison,

I tried it but had too much of the N2 tail affecting the CO downstream (as
both are m/z 28 of course).  Perhaps it might be best to pack them twice and
combust for the 15N separately or setup pyrolysis with a switching
("Brooks") valve to divert the N2 tail before the CO arrives.

Bob

------------------------------------------------
Robert D. Stickrod II, Lab Manager
Idaho Stable Isotopes Laboratory
  www.cnr.uidaho.edu/isil
Department of Forest Resources
College of Natural Resources, Room 214
P.O. Box 441133, University of Idaho
Moscow, ID 83844-1133, U.S.A.
[log in to unmask]
lab: (208) 885-6512
fax: (208) 885-6226
cell: (509) 338-2814
------------------------------------------------


>From: Alison Bateman <[log in to unmask]>
>Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] pyrolysis of silver nitrate for 15N and 18O
>ratios measurements
>Date: Fri, 30 May 2003 10:17:10 -0400
>
>Dear Cecily,
>
>We are looking to develop a pyrolysis system so that
>we can measure the d18O composition of AgNO3 after
>extraction of nitrate from solutions using an anion resin.
>
>Since we are in the early stages, we would be interested
>to hear your thoughts about the 'problems' that you
>encountered when you tried to run samples by pyrolysis.
>
>Many thanks,
>Alison Bateman.
>
>++++++++++++++++++++++++++++++++++++++++++++++++++++
>Alison Bateman
>School of Environmental Sciences
>University of East Anglia
>Norwich
>NR4 7HU
>UK
>
>[log in to unmask]
>
>++++++++++++++++++++++++++++++++++++++++++++++++++++
>
>
>
>On Wed, 28 May 2003 13:26:22 -0700, Cecily C Chang <[log in to unmask]>
>wrote:
>
> >Dear All,
> >
> >      A comment about using the column method for pyrolyis. We typically
>do
> >not run samples by pyrolysis. On the few occassions that we have run
> >pyrolysis samples, there were problems.
> >
> >      If you follow the instructions there should be no problem. Chang et
> >al. 2002. CJFAS also describes using a cation column to minimize the
> >organic load.  If you overload the column, if the silver is not clean,
> >there will be a problem. You must check the silver nitrate for background
> >nitrate. It takes us many weeks to clean silver.
> >
> >
> >
> >Cecily
> >
> >
> >
> >Cecily C.Y.Chang
> >Hydrologist/Ecologist
> >Stable Isotope Tracers Project
> >345 Middlefield Road
> >USGS Mailstop 434
> >Menlo Park, CA 94025
> >650-329 4471  Fax 5590
> >[log in to unmask]
> >
> >"They that can give up essential liberty to obtain a little temporary
> >safety deserve neither liberty nor safety."
> >
> >                                                     ----Benjamin
>Franklin
> >
> >
> >
> >
> >                      Teppei Fukada
> >                      <[log in to unmask]        To:
>[log in to unmask]
> >                      UK>                      cc:
> >                      Sent by: Stable          Subject:  Re: [ISOGEOCHEM]
>pyrolysis of silver nitrate for 15N and 18O ratios
> >                      Isotope                   measurements
> >                      Geochemistry
> >                      <[log in to unmask]
> >                      UVM.EDU>
> >
> >
> >                      05/21/2003 01:13
> >                      AM
> >                      Please respond to
> >                      Stable Isotope
> >                      Geochemistry
> >
> >
> >
> >
> >
> >
> >
> >Hello,
> >
> >I am sorry for my irresponsible last e-mail.
> >What I referred as "microbial method" in last e-mail is "denitrifier
> >method, and
> >the references are
> >
> >Cascioti, K.L., Sigman, D.M., Galanter Hasting, M., Böhlke, J.K. and
> >Hilkert, A. 2002. Measurement of the oxygen isotopic composition of
>nitrate
> >in seawater and freshwater using the denitrifier method. Anal. Chem. 74,
> >4905-4912.
> >
> >Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, M., Galanter, M.
>and
> >Böhlke, J.K. 2001. A bacterial method for the nitrogen isotopic analysis
>of
> >nitrate in seawater and freshwater. Anal. Chem. 73, 4145-4153.
> >
> >
> >Thanks,
> >
> >
> >
> >Teppei
> >
> >
> > ----- Original Message -----
> > From: Rodrigo Maia
> > To: [log in to unmask]
> > Sent: Tuesday, May 20, 2003 10:24 PM
> > Subject: Re: [ISOGEOCHEM] pyrolysis of silver nitrate for 15N and 18O
> > ratios measurements
> >
> > Teppei
> >
> > How about giving a reference for the benefit of all on that "microbial
> > method"???
> >
> > Rodrigo
> >
> > Rodrigo Maia
> > Lab Tech
> > Stable Isotopes Lab - ICAT Lisbon
> > Portugal
> > [log in to unmask]
> > -------Original Message-------
> >
> > From: Stable Isotope Geochemistry
> > Date: terça-feira, 20 de Maio de 2003 19:24:33
> > To: [log in to unmask]
> > Subject: Re: [ISOGEOCHEM] pyrolysis of silver nitrate for 15N and 18O
> > ratios measurements
> >
> > Hello,
> >
> > How about measuring the gas product by gas chromatograph?
> > How do you eliminate organic matters in the samples?
> > Have you checked the Cecily Chang's method? Have you washed
> > Ag2O before using it?
> > How about eliminating anions using BaCl2 before the anion
> > exchange NO3 absorption?
> >
> > How about the new microbial method?
> >
> >
> > Regards,
> >
> >
> > Teppei
> > ----- Original Message -----
> > From: Eddy Minet
> > To: [log in to unmask]
> > Sent: Tuesday, May 20, 2003 6:24 PM
> > Subject: [ISOGEOCHEM] pyrolysis of silver nitrate for 15N and 18O ratios
> > measurements
> >
> >
> >
> > Hi,
> >
> >
> > Here are some of my recent problems, and I hope you may bring me some
> > answers.
> >
> >
> > I work on the measurement of 15N and 18O ratios in silver nitrate.
> > Nitrates originate from groundwater and have been extracted using the
> > technique issued in Silva S.R.., Journal of hydrology, 228 (2000), 22-36
> > (i.e. using anion exchange resin with final neutralization by silver
> > oxide). The isotopic ratios are measured by pyrolysis, with the furnace
> > temperature around 1100 degrees for 15N analysis (Roboprep CN) and 1450
> > degrees for 18O (ThermoFinnigan TC/EA).
> >
> >
> > The reproducibility on both 15N and 18O has been a bit disappointing so
> > far.
> >
> >
> > In relation to 18O analyses, the CO peak looks always okay whilst the N2
> > peak (that appears for m/z 28 just before the CO peak) can have a very
> > strange shape, or just trails and even sometimes overlaps the CO peak.
> > Whenever this first peak (N2) looks funny, and even if it doesn't seem
>to
> > overlap the CO peak, the resulting 18O ratios hits the roof and can rise
> > up to +75 per mil when other replicates would show up around +6 per mil.
> >
> >
> > As for 15N analyses, the reproducibility is much better (standard
> > deviation usually within 0.5 per mil), but results are far from what is
> > usually achieved when analyzing some organic samples. Addition of some
> > sucrose seems to improve a bit, but still?
> >
> >
> > At the end, we are wondering whether the problem is just a matter of
> > sample homogeneity (my silver nitrate samples look a bit like fibers or
> > wool). I'll try very soon to grind finely some samples after freezing
>them
> > with liquid nitrogen to see if there is any improvement. Nevertheless I
> > would appreciate to know if anyone of you has already experienced these
> > problems and managed to work them out.
> >
> >
> > All the best,
> >
> >
> > Eddy Minet, Ph.D. student
> >
> >
> > Centre for the Environment
> >
> >
> > Trinity College
> >
> >
> > Dublin 2 (Ireland)
> >
> >
> > Tel: +353 (0)86 827 4921
> >
> >
> > Email: [log in to unmask]

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