Hi Paul,


Thanks for the reply.  Can you shoot me your vendors off list for your
0.5mm ID tubes and zero dead volume fitting?  I absolutely hate how many
tubes I break every time I need to change the reactor and would be
forever grateful if there is a way to avoid this.  I would even go so
far as to say you would deserve some kind of international humanitarian
award for this information!


Regarding the peak broadening issue, this is also something I've
considered, but I guess I've always assumed that the transition from a
small diameter capillary to the large diameter ceramic tube would trump
the turbulence introduced by the wire in terms of chromatography (but I
could be absolutely wrong, just my assumption).  


Thanks again for the thoughtful comments.





From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
Behalf Of Paul Eby
Sent: Wednesday, March 26, 2008 5:12 PM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] DIY Oxidation Reactor -- Better Chromatography
with Smaller Tubes?



You need not reduce your tubing OD. With a proper zero volume fitting,
it can be any size you desire without affecting the chromatography. We
have built our ovens around a 1/8" OD ceramic tube (0.5mm ID) and no
longer worry about breaking tubes as we tighten fittings.

Also, I've often wondered though if the peak broadening due to ovens
isn't more due to the wire in the tube than the ID of the tube. Does the
wire cause broadening by disrupting laminar flow?

Paul Eby
University of Victoria 

At 01:47 PM 26/03/2008, you wrote:

Has anyone had experience with building their own oxidation reactors
with smaller ID tubing to improve their chromatography during the
combustion process?  I know how much of a pain it is to change these
reactors, and while a smaller ID/OD tubing will probably increase the
chances of breakages during replacement (not to mention potentially
decrease the life span of the reactor), for certain types of analyses
the performance gain may make up for it.
Also, is there a reason most users go with the 0.1 mm wires instead of
something a little thinner (say 0.05mm) to increase the packing
efficiency (and thereby reduce dead volume) and also surface area? 
I have to admit that this is the first time I've ever had to purchase
reactors from Thermo (I inherited a stock from the previous technician)
and I actually laughed at the customer service rep who gave me the price
over the phone...
Thanks in advance,
Michael D. Kubo
NASA Ames Research Center
M/S 239-4
Bldg. N239, Room 327
Moffett Field, CA 94035
(650) 604-6110