We had an undergraduate student doing a variety of experiments to test the
EA efficiency (varied temperature, sample size, amount of C/N, amount of
acid to add to soils to remove inorganic C, etc.) last year. I would like to
put those results on our webpage (or the wiki page), but I first need to let
him write it up and present it.

One test we performed to check on the combustion efficiency of low C,N
samples was to take a peach leaf standard and add powdered obsidian (no C or
N content) to it to verify that isotope ratios were ok with samples as big
as about 45mg. I don't see why this experiment couldn't be carried out to
200mg. I can send you some of the data if you'd like to give you an
illustration of what we did.

Hopefully I'll be able to post the student's results in the next month or
two. The data are more than one year old now...

Anthony


------------------------------------------------------
Anthony L. Michaud
W. M. Keck Foundation Laboratory for Environmental Biogeochemistry
School of Earth and Space Exploration
Arizona State University
Tempe, AZ 85287-1404
 
Web: http://kfleb.asu.edu
Tel: 480-727-8033
Fax: 480-965-8102
 
Mailing address:
 
Anthony Michaud
PSF-686
Arizona State University
Tempe, AZ 85287-1404
 
***Windsurf Everywhere***
------------------------------------------------------
 
-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Isabelle Billy
Sent: Wednesday, February 21, 2007 2:47 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Good soil combustion

Dear all,

I 'm so concerned, as we have often the same problem with some sediment 
wich are very poor in N (0.02%), so I'm really interesting in the 
answer, as I often doubt that we have a good combustion with 100 or 
200mg sample.


Ruben G. Chavez a écrit :

>Dear all, 
>
>I am analyzing SOIL NC in EA and I need at least 75ugN in the sample to get
a 
>good linearity. With this amount of N I need, I need to weigh up to 200 mg
of 
>finely ground sample due to low %N in the sample. Please help me on how to 
>know if I have a good combustion of the sample. Is there a specific 
>combustion catalyst for plant or soil combustion?
>
>Many thanks for your help.
>
>
>Ruben G. Chavez
>Officer
>Analytical Service Laboratories
>Mail: DAPO Box 7777, Metro Manila, Philippines
>Tel: +63(2) 580-5600 ext. 2419
>Fax: +63(2) 580-5699
>Web: www.irri.org
>
>  
>

-- 
Isabelle Billy
UMR EPOC - 5805 
Département de Géologie et Océanographie
Université de Bordeaux I
avenue des facultés
33405 TALENCE Cedex, France

email [log in to unmask]

tel. (33) 05 40 00 33 14
fax (33) 05 40 00 08 48