David Halsall wrote:
>We are having problems performing correlation analysis on data
>obtained from GC chromatograms. As the extraction efficiency of the
>samples is highly variable we are expressing individual peaks as a
>percentage of the total peaks area.
Probably you mean the extraction of the analyte(s) from the sample material
(blood, urine, other?) before injecting into the GC column.
Hence, the problem is this variability, and primarily the extraction process
should be improved. Maybe you already have tried several extraction methods
have found that this is not possible.
Probably all analytes extract poor but proportionally from your sample. This
is not necessarily true and you have to prove it.
If it is true you can arrange the extraction process in such a way that you
always get a sufficient concentration for each component of interest in the
extract to get peaks above LOD.
Frequently this will yield extracts with too high a concentration, and then
you must dilute it before injection. By spiking the sample with a
tritium-labeled component you can easily determine how much the extract
should be diluted.
If a I-125 labeled tracer is available the whole extract can be measured
without loss of material due to mixing with scintillation fluid.
Yours
Mr Sten Öhman, PhD
Elfin Lab & Milieuconsult - Part of the Wiltag group
E-Mail address: [log in to unmask]
Telephone int: +46 13 368941, Nat: 013-368940
Fax int: +46 13 368941, Nat: 013-368941
Mobile tel: 0709-526415
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