This is more of a GC/MS question but I was hoping someone might have
some insight into my problem. After a period of low use on the GC/MS, we
recently replaced the MS filament and cleaned the MS. We are observing a
series of siloxane peaks in the hexane blanks (see attached).
Interestingly, there is no observable siloxane contamination when BSTFA
blanks are run. We have used 2 different lots of GC grade hexane, one of
which I have previously used and had no contamination. Both lots produce
virtually identical chromatograms. I have replaced the septum, inlet
liner, syringe, and replaced the column. The problem is replicated with
the new column (which was previously fine). Columns are Restek RXI-5MS
and RXI-5 Sil MS.
Any thoughts as to what might be causing this would be much appreciated.