Colleagues: This is a GC/MS issue, but hopefully some of the recipients of this
email are familiar with issues pertaining to GC/MS
We are using our GC/MS (Thermo orbit rap instrument) to identify compounds
extracted from the surfaces of ancient ceramics. We extract ground material
with chloroform/methanol (2/1), dry the extracts in a vacuum centrifuge,
complete drying by adding benzene and drying again in the vacuum centrifuge,
then treat the samples with methoxyamine HCl in pyridine, dry the samples again
and treat them with BSTFA/TMCS. The GC.MS profiles reveal the variable
occurrence of two contaminants that closely co-elute. One is a brominated
decane ( the ions at 134 and 148 in the attached file) and the other (the ion
at 257) at the moment is unknown. We have been unable to identify the source
of these contaminants. They occur with variable frequency, and sometimes are
intense. The contaminants have never been observed following solvent (ethyl
acetate) injections, so the instrument does not appear to be the source. In
the most recent experiment we were unable to predictably re-create the
contamination by substituting in and out the various stages of the method. The
contaminants appear regardless of the stages deleted or added. We need advice
as to what might be the source of these contaminants. Any and all suggestions
are welcome
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> Kym and Jacob
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> Kym Francis Faull, Ph.D.
> Director, Pasarow Mass Spectrometry Laboratory
> Jane and Terry Semel Institute for Neuroscience and Human Behavior at UCLA
> Professor Emeritus, Department of Psychiatry and Biobehavioral Sciences
> David Geffen School of Medicine at UCLA
> Telephone: (310) 206 7881 (office)
> Telephone: (310) 206 7886 (laboratory)
> Facsimile: (310) 206 2161
> Electronic mail: <email obscured> <email obscured>>
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