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Non-identifiable problem in GC/MS: unusual He consumption and no leaks detected

Question asked by lmarsan on Mar 19, 2019
Latest reply on Jan 15, 2020 by vjpugal

Dear all,


We've been experiencing some problems with our GC/MS system (GC Agilent 6890N and MS Agilent 5973), coupled to a double-shot pyrolyser (model 2020i; Frontier Laboratories). Under normal conditions and regular use, the He bottle used to last between 6 and 12 months, whilst ca. 5 months ago it only lasts 3 months or even less. We all are conscious of how costly ordering frequently a He bottle is. On November I asked a related question in this forum.

Once we detected that the He bottle was depleting to an unnormal rate, we started to replace and adjust any consumable that could affect this. Furthermore, it was observed how the needle of the pressure gauge slightly fluctuates while the device is on. This problem was solved when we changed the Cu tubing from the bottle to the GC, solving the welding problem, but still, the rate at which He bottle drops out is not usual by far.


Here's a list of the replaced consumables:


*O-ring for a simple base of Py-2020iD

*Interface needle

*Quartz tube y corresponding o-ring and washer.

*Graphite vespel ferrule

*Interface Union needle



* Cu tubing that goes from the He bottle to the GC, along with the SWAGELOK 1/8” fittings.

* DB-5 GC column was cut in both extremes, inlet and MS line zones, in case there was any obstruction. At the same time, fittings and correspondent graphite ferrules were replaced.

* Liner Splitless: Gold Plated Inlet Seal with Washer, injector line septum, and Cu tubing from Splitless.


Ultimately, we tried two internal leak tests according to the manual, and both resulted negative. Everything seems to be right but the abnormal He consumption keeps going.


Can anyone that experienced a similar problem suggest me where could be the problem? I read in some forums that it could be a problem related to the EPC; if so, then what we could do?


Thanks in advance and kind regards,