You may try a static pressure test to ensure that the leak is indeed from the TCEA. To do this, cap off the exit from the GC before the carrier gas travels to the Conflo, then quickly cut off the He supply to the TCEA (a two-way valve just upstream of the TCEA is convenient). If there is no leak, the pressure on the TCEA should not decrease. Give it some time to present itself.... If the pressure does drop, you can try this again, now capping off the entrance to the GC. No pressure drop this time = leak associated with GC. If the pressure drops, I'd keep going backward toward the reactor.
Bethany P. Theiling, Ph.D.
Caltech Postdoctoral Scholar
Jet Propulsion Laboratory
4800 Oak Grove Drive.
Pasadena, CA 91109
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Elliot Desilets
Sent: Friday, March 06, 2015 11:45 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] TCEA Background Issues
I am having great difficulty in getting our system to spec with regards to background levels. We will be using it for D and 18O analysis in urine and saliva samples. We have a thermo TCEA coupled to a Conflo 3 and a Delta V Plus. The TCEA has not been running for roughly 9 months. We have installed a new glassy carbon reactor, ceramic tube and bottom feed adapter. Peak centre levels are as follows: 40 @ 552mV, 28 @ 27850 and 32 @ 6400.
Spraying Ar on the fittings has not helped to identify the source of a potential leak, as spikes were not observed on 40. Also, when we close the TCEA from the Conflo, the levels drop (Ar ~ 50mV), indicating that the source of the background is indeed coming from the TCEA.
He and H2 tanks were recently replaced and the background levels did not improve. The capillaries in the conflo are all at the required heights as well.
We have tried baking the GC column to 300 overnight and that improved the background somewhat, however upon cooling to operational temp, we got an error code "1999". We had to cool the reactor and re-start the system. The code went away, however, when we tried to ramp up to 300 again to bake, the code appeared again and we had to re-start again. It seems to work at operation temp (90) however I do not know the extent of the damage.
We have also baked the reactor at 800 over a weekend and that also improved the background levels, however they have seem to have stabilized.
We are running out of ideas and any help would be much appreciated.
Richardson Centre for Functional Foods and Nutraceuticals University of Manitoba Winnipeg, Manitoba, Canada