Contamination from ferrules?

[EricD]

I am running a PFPD for sulfur analysis, and I'm finding a consistent contamination of CS2, but also I suspect for COS.

The entire system is either silcosteel, teflon, or the column. So, I suspect the ferrules (vespel). Does anyone know of references to or experience with contamination from ferrules?

Thanks

[Mark]

EricD,

Just out of curiosity, how do you know what the contaminants are? If they were from the ferrules I would expect you to have a fairly constant background. I ran an SCD for awhile using vespel ferrules and don't remember any problem with a sulfur background from the ferrules.

Rgeards,
Mark

[Amirav]

Graphite ferruls provide significant sulfur background for many hours/days even after heating to 300C. Vespel graphite is much better. However, the ferrules produced sulfur background is continuous and not in the form of peaks (unless in the injector side of the column.
Poor quality air contains trace amount of SO2.
Usually the extra sulfur peaks are from your sample that find its way to dead volumes in the injection and sample path. Some columns develops activity to active sulfur compounds such as H2S and thiols and thus emit them as background at the high temperature end of chromatogram
AA