Dear Listmembers I have another question that I hope is of interest to some
readers.
We had last year a visitor to our lab. who recounted that for continous flow
analysis, he used a much reduced helium carrier flow rate of some 30ml/min,
so gaining sensitivity in N2 response - an advantage for very small samples.
Upon trying this for myself I get the increased peak area response as
advertised, yet get no significant improvement in the sample size limit of
isotope determination.
The question is, what is required to happen to improve the limit of
measurement? Is it lower sample dispersion in the gas chromatograph, or
simply greater residence time in the MS? In my case, the improvement in
chromatography was minimal, (as measured by peak height per unit sample
size) so then should little improvement be expected? If has anyone got
experience with fine-tuning of these big-bore GC columns, I would be interested
to hear.
Thanks
Mr. Robert Van Hale
Chemistry Department
University of Otago
PO Box 56
Dunedin
New Zealand
Ph (+64)(03)479 7908
Fax (+64)(03)479 7906
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