Paul,

this is interesting. We have done similar experiments and find a nice linear
relationship between the D+ beam area and concentration in the range 20-200
yg N. However, we have not been investingating this relationship for higher
concentrations of N (and C).

Per Ambus
Plant Biology and Biogeochemistry Department
Risø National Laboratory
DK-4000 Roskilde
www.risoe.dk/pbk


-----Original Message-----
From: Paul Brooks [mailto:[log in to unmask]]
Sent: 14. juni 2000 20:05
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] total N and total C in solid samples


> >Peter, I am sorry it has taken me so long to respond to this, but I have
>been doing experiments on this exact problem.
> >
> >With either our Europa Sci. 2020 or our FM Delta Plus we have the problem
>that the response curve of the mass spectrometer in terms of beam area to
>concentration is not linear.  When using the TCD on a Carlo Erba the
>response is essentially linear at least over an order of magnitude.
>However, my Europa doesn't have a TCD and the Delta plus software cannot
>read the TCD on the Carlo Erba.  Therefore, I run 10 variable weight
>standards during a run and then fit a polynomial curve to the response,
>then adjust the unknown samples accordingly.  This seems to compare well
>for % data to that from a regular Carlo Erba with TCD.
> >
> >I can send you additional details if you like.
> >
> >Please send any personal response to [log in to unmask] which
is
>our new centers email address.
> >
> >Paul.
> >
> >
> >
> >At 01:45 PM 5/26/00 +0200, you wrote:
> >>Hi all,
> >>
> >>We have started measuring atom% N and atom% C in solid
> >>samples (soil and plant material) a while ago, using PDZ Europa's
> >>ANCA-SL coupled to the 20-20 mass spectrometer.
> >>
> >>We would like to start measuring total N and C content also, but
> >>we don't really know what kind of reference material we should use.
> >>Is it possible to send me some tips on this analysis? What is the
> >>best way to do it?
> >>
> >>Thank you very much.
> >>
> >>Peter.
> >>-----------------------------------------
> >>Peter Vervloedt
> >>Ghent University
> >>Laboratory of Applied Physical Chemistry
> >>Coupure Links, 653
> >>9000 Gent
> >>tel.: +32 9 264 60 00
> >>fax.: +32 9 264 62 30
> >>e-mail: [log in to unmask]
> >>----------------------------------------
> >>
>
>
>
>Paul D. Brooks.
>
>Dept. ESPM-Ecosystem Sci.,
>151 Hilgard Hall, MC 3110,
>UC Berkeley, Ca. 94720-3110.
>
>phone (510)642-3155
>FAX   (510)643-5098 (to Att. Paul Brooks)