We recently experienced the same symptoms. We traced the leak to the
x-fitting in the GC. Try replacing the ferrules and reinstall the
capillaries at the x-fitting.
Georges L. Paradis
Analytical Lab Manager
Marine Science Institute
Bldg 520, Room 4013
University of California Santa Barbara
Santa Barbara, CA 93106
805-893-7182 (ICPMS lab)
805-893-3802 (MSI lab)
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Tim Sobolevsky wrote:
> Dear colleagues,
> as a newbie to the field of GCC-IRMS, I may not understand some basic things,
> but I have found a leak in my system that I cannot explain nor cope with it.
> The system is Trace GC / Combustion Interface III / Delta V Advantage,
> intended for analysis of steroids.
> When switching from straight mode to the backfkush, if open split remains "in",
> I see a short but intense leak. Monitoring mass 40 at cup3, the intensity may
> reach 1.5V for a moment of several seconds (mass 28 at cup3: up to 10V).
> The intensity depends on how long the backflush valve was closed (the signal
> maybe 300 mv Ar or something if I close it for 10-20 sec), and the time lag
> between backflush opening and seeing the leak in mass spec is ca. 5-7 sec.
> I disassembled the valve and replaced the vespel seat and PTFE seal.. sprayed
> Argon near every suspicious place.. closed the restriction capillary at SGE
> valve with septum.. connected the valve to the argon tank instead of
> pressurized air - all this did not change a bit.
> Additionally, I 've tried to exclude the GC part by making helium to flow as
> follows: sge valve -> reduction furnace -> nafion -> open split. All in vain until
> Sorry if I gave to few technical details, I promise to improve myself..
> Tim Sobolevsky, PhD
> Senior Analyst
> Moscow Anti-Doping Center