GC Sandwich Injections: How to deal with vial septa?
Greetings fellow nerds!
I am playing around with our Agilent GC 7890B (both an FID and an MS) functionality to do layered injections, particularly for in-port TMS derivatization (currently experimenting with different reagents). So far, I like the results. However, one notable problem is the septum on the reagent vial cap. It's a vial with a 200 uL insert containing 100 uL reagent. With our usual Red Rubber // FEP 1.0 mm caps, eventually, strong polysiloxane peaks appear in chromatograms. Which is interesting, since I can usually inject the same sample near endlessly without this happening. I also tried aluminium septum caps, but predictably, the reagent evaporates overnight.
I wonder how people deal with this except by replacing the caps every couple injections. During long sequences that go on for days, this seems awfully impractical. Are there caps that are better suited?
Thanks to all in advance!