Dear Sergine,
> I would like to measure the d15N of the aminoacids Arg and Gly (separately)
> in a mixture of several aminoacids, and possibly other nitrogeneous
> compounds. I guess this is possible with the GC-C-IRMS technique, but I
> have never used it.
You guess correctly.
> I would be very grateful to anybody who could ask one or several of the
> following questions :
>
> - is it possible or do I have to purify Arg and Gly from my mixture before?
> - what is the minimum amount of matter needed per measurement?
> - who does this kind of analyses and how much does it cost?
There is a good chance that you can inject your AA mixture (protein
hydrolysate?) straight on to the GC, after the usual clean-up and
derivatisation steps.
The question about minimum amount on column per individual amino acid
necessary depends whom you speak to. Instrument manufacturers are
like Microsoft, they give you the minimum amount under the best
possible conditions (downhill with the wind in your back). It is
possible to do d15N analysis with 1 nmol (and less) per amino acid
injected (splitless) on to the GC but I wouldn't recommend using this
as a goal post. Unless you have to because your original sample can't
be larger than X (e.g. human samples such as blood, tissue etc.).
I would aim to inject at least 2 nmol per individual AA, preferably 4
nmol, to ensure that 250 pmol to 1 nmol of N2 actually end up in the
ion source (this is assuming 100% conversion and no N-oxides plus a
split of 1:4 prior to the ion source).
For references as to sample preparation, derivatisation,
GC-conditions and all that sort of apple sauce have a look at:
C.C. Metges et al., J. Mass Spectrom., 31, 367-376 (1996)
C.C. Metges and K.J. Petzke, Anal. Biochem., 247, 158-164 (1997)
T. Preston et al , Br. J. Sur.,. 82, 229-234 (1995)
C.L. Williams et al., FEMS Immunol. Med. Microb, 13, 87-94 (1996)
I.A. Simpson et al., Archaeol. Prospect., 4, 47-152 (1997)
W. Meier-Augenstein, LC-GC, 15, 244-263 (1997)
W. Meier-Augenstein, J. Chromatogr. A, 842, 343-363 (1999)
and my webpage on AA derivatisation (for URL see below).
Hope this helps.
Regards,
Wolfram
****************************************************
Dr. W. Meier-Augenstein, CChem MRSC
Senior Research Fellow
University of Dundee, Dept. of Anatomy & Physiology,
OMS, Small's Wynd, DUNDEE DD1 4HN, United Kingdom
Tel.: +44-(0)1382-34/5124, /4574, /4968
Fax: +44-(0)1382-34/5514
e-mail: [log in to unmask]
URL: http://www.dundee.ac.uk/anatphys/wma/wolfram.htm
NB Message is confidential and for recipient only: Unauthorized reading and copying
may result in legal action! Opinions expressed those of author not institution.
LEGAL NOTICE: Unless expressly stated otherwise, this message is confidential and
may be privileged. It is intended for the addressee(s) only. Access to this
e-mail by anyone else is unauthorized. If you are not an addressee, any
disclosure or copying of the contents of this e-mail or any action taken (or not
taken) in reliance on it is unauthorized and may be unlawful. If you are not an
addressee, please inform the sender immediately.
|
