If you haven't already done this as part of your inlet cleaning, you might replace the seal at the base of the inlet. I've seen bits of septum on the seal produce siloxane peaks.
Summons Geobiology Lab
Massachusetts Institute of Technology
45 Carleton St
Cambridge, MA 02142
From: Stable Isotope Geochemistry [[log in to unmask]] on behalf of Marshall Woodworth [[log in to unmask]]
Sent: Tuesday, May 31, 2016 8:32 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Siloxane contamination
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.