Good Morning/ afternoon everyone!.

We have been experiencing a problem with our Delta+XL  Trace TC/GC system 
running (at the moment) Methane for Hydrogen Isotopes.

While reproducibility is good as are Stability and H3 values (6.5ish) we have a linearity 
drift of 10+ per mil between high and low injection sizes - I am not worried too much 
about this as it seems steady and reproducible so can be corrected for if need be.

However, increasing the GC temp (55C to 100C) will shift the values some 15-20 per 
mil (more positive). It also changes (cleaves) the 3/2 ratio trace somewhat). You can 
see the potential problem when we want to look at any other hydrocarbon fractions that 
would involve temp ramping.

Since we are still new to the system, we are a little lost as to "WHAT IS NORMAL"?. 

We have spent the last weeks doing the more obvious things, changing
septa syringes, liner cleaning and leak checks. We have also replaced
guard column and swapped the column (CarbonPlot) as well but the troubles
seems to remain with the same temp effected, floating values.

While doing are swapping of bits listed about we sprung a major leak related to the 
furnace tube and/or connections. We took this opportunity to put in a new Aluminium 
Oxide and remove potential issues with it. We are still seeing this shift - back to square 
one - which has lead me to call out for assistance.

Tuning mass 18 in the cup 29 gives a water peak of 540mV (higher then the <300mV 
listed but not a panic situation) and mass 30 in the 30 cup at 145mV (which is oddly 
higher then the 30-50mV listed). These could indicate nafion troubles and the NO 
mass30 may indicate reduction over (Cu) death. This is bypassing the GC flow 
(backflush open) and through the GC Combustion lll unit.

1) If we are not using the Red reactor (@ room temp) can is still poison the makeup He 
stream?

2) How much shifting would you expect (if any) in hydrogen values with GC
temp manipulation?

3) Can you get really bad linearity even though the H3 and On-Off
Stability looks good?

Sorry for the long ramble but I am hoping to provide you all with as much info as
possible.

Hope you're all having a better time then we are heheh.

Cheers,


Bill Mark
Isotope Technician
Environmental Isotope Lab
University of Waterloo
Phone (519)-885-1211 Ext 6747
FAX (519)-746-0183
http://sciborg.uwaterloo.ca/research_groups/eilab