Hi Eric
Thank you very much for your reply.
What is the detection limit of your Isolink HPLC-IRMS in terms of VFA  
(primarely acetate) concentration and 13C enrichment?

Perhaps we (Britta Gribsholt and I) could come and take a look at your system
-and maybe have a few samples analyzed?

Best
Nils

Citat af "Boschker, Eric" <[log in to unmask]>:

> Hi Nils,
>
> We have measured VFA labeling in porewaters by GC-MS (see for instance
> Boschker et al. FEMS Microbiology Ecology 35 (2001) 97-103 and
> references therein). The method works well for brackish and freshwater
> samples, but you may run into trouble with marine sediments due to the
> high salt deposites that form within the GC injector. You may need to do
> things like microdestillation to get rid of the salts. The sensitivity
> of the method depends more on the actual concentration of 13C-VFA in
> your sample than on the percentage 13C excess. Think of 1 to 3 microM
> 13C-VFA that can be detected, but this was on an rather old HP MSD.
>
> Currently, we are using the Finnigan Isolink HPLC-IRMS for this purpose
> and I have to say that it works much easier in terms sample treatment
> and 13C sensitivity etc.. But at a price.
>
> Greetings,
>
> Eric Boschker.
> -----------------------------------------------------------------------
> dr. H.T.S. Boschker
> Netherlands Institute of Ecology (NIOO-KNAW)
> Centre for Estuarine and Marine Ecology
> PObox 140, 4400 AC Yerseke, The Netherlands
> Visiting address: Korringaweg 7, 4401 NT Yerseke
> Phone: +31 113 577493/300
> Fax: +31 113 573616
> mailto:[log in to unmask]
> http://www.nioo.knaw.nl/PPAGES/eboschker/
> -----------------------------------------------------------------------
>
>
>
> ________________________________
>
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> Behalf Of Nils Risgaard-Petersen
> Sent: Tuesday, November 11, 2008 4:15 PM
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] GC-Ms for VFA
>
>
>
> Hello
>
> We are currently in the process of getting equipment for analysis of VFA
> at low concentrations in sediment porewater. Both Thermo and Analytical
> Instruments recommend GC with either a FID or a single quadrupole MS.
> We would also like to measure the 13C enrichment of samples spiked with
> e.g. 13-C acetate (expected enrichment: app 10%) . We have received
> conflicting information about the ability of the single quadrupole MS to
> measure 13-C acetate. Does anybody have experience with 13-C on a single
> quadrupole MS. The alternative is of cause IRMS but this is much more
> expensive.
>
>
>
> Thanks
>
> Nils
>
>
>
> Nils Risgaard-Petersen, Ph.D.
>
> Center for Geomicrobiology
>
> Institute of Biological Sciences
>
> University of Aarhus
>
> Ny Munkegade bldg. 1540
>
> DK-8000 Aarhus C
>
> Denmark
>
> Phone: ++45 8942 26 97
>
>
>
>