a lot of siloxanes, contamination, column, beed, etc.?
Posted: Mon Aug 13, 2012 6:50 pm
by adsfo
I'm getting a lot of various siloxanes eluting (heptasiloxane, tetrasiloxane, etc.). I tried different columns and replaced liner and septum. Any idea where those siloxanes are originating from?
Re: a lot of siloxanes, contamination, column, beed, etc.?
Posted: Tue Aug 14, 2012 12:41 am
by Don_Hilton
Did you clean the inlet and do you have septum purge flow?
Siloxanes come from lots of places. These include septa and columns - and even vial cap speta.
If you inject from a vial and let it sit over night, you may find that you have an unacceptable siloxane level - just from what leaches out of the punctured septum.
Siloxanes will make it into the injection port if you do not have the septum purge flow operating and will make it into the injection port as crumbs falling from the septum as injections are made. If you have packign in the liner, you may catch most of the crumbs on the packing, but some may bake it thorugh to the seal plate (which ocasionally needs to be changed). And depending on levels in your inlet in the past, you may (or may not) have to worry about migration. (Clean with solvents if you are worried.)
The column is a source of siloxanes, as you know.
And, I have begun to supect that siloxanes make it into the laboratory as contamination on packing materials, given that silicone oils are so widely used for all kinds of things.