We used to have tailing or fat peak problem of CO with our Isoprime-EA. It
turned out to be the aging glassy-C tube that got more or less porous and
absorb CO. The situation is much worse for water samples then solids. We
changed a new carbon tube and the problem was gone.
----- Original Message -----
From: "David Harris" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, December 16, 2004 11:36 AM
Subject: [ISOGEOCHEM] CO peak tailing
>I have a TC-EA system based on the Hekatech furnace with glassy carbon tube
> in ceramic tube design. It used to work fine. Now I have severe tailing
> of the CO peak which I have been unable to cure. I'm out of ideas as to
> what to try next.
> Here are some things I have already tried.
> 1. The tailing is similar whether I try organic (eg sucrose) or inorganic
> (eg silver nitrate) samples.
> 2. Changing the reactor temperature between 1200 and 1400 has no effect
> 3. Baking the molecular sieve GC column did not help
> 4. Reassembing the reactor numerous times including replacing the glassy
> carbon tube and filling (130 mm GC 'chips' sieved to 2.5-3.5 mm + 5mm
> layer nickelized carbon) had no effect.
> 5. Increasing the spring loading on the glassy carbon tube did not help -
> the theory here was that the balance of gas flow through the inner and
> outer tubes was incorrect and that more spring pressure would increase the
> flow through the inner tube.
> 6. The system is leak tight and has a low background and blank.
> What really gets me is that nothing I have tried so far had any effect -
> any ideas most welcome
> David Harris
> UC Davis Stable Isotope Facility
> Department of Agronomy
> 3112 Plant & Environmental Sciences Bldg.
> Davis, CA 95616
> phone 530 754 7517
> fax 530 752 4361