Hi Shelley
There are indeed many different trapping techniques as you can see by Willi and Pier's comments and references.  Many of the references are from the Dual-inlet techniques where the amount of gas is very low and you do not have a carrier (e.g. Helium).  The main thing you have to be careful with is the fact of the helium carrier's presence.  In some cases we can see (glass trap) the frozen gas of interest (e.g. CO2) slowly creep through the trap as the hot helium flows through.  The higher the flow, the more heat and carrying possiblility of the "ice" sample being fractionated by the "hot wind".  The key is in the tubing diameter and it's lenght.  For a fused silica capillary (e.g. 0.32 mm ID)in a GC type of flow  (2-3ml/min) it can be relatively short.  From the EA we tend to have stainless steel 1/6" OD (ID can vary) tubing and flows between 80-120ml/min; where thw helium comes out around 60oC.  If you make a double loop or spring type trap it should be fine for the lenght of time you want to trap and release (about 1m lenght should do it).

As for the trigger to the trap, the ConFlo still has all commands of the 8 valves available.  You need to find the right wire and add your own solenoid with the proper rating(24V, xW)and attach it to a piston onto which your trap can be raised or lowered.  

In Isodat you can add this trap to the ConFlo drawing and device, or have it as it's own device, and have it available in the Time Events for your method which will allow you to automate it.  None of this requires ISL or programming knowledge.

Have fun
Gilles

Gilles St-Jean
Chercheur / Research Scientist
Université d'Ottawa / University of Ottawa
Sciences de la Terre / Earth Sciences
140 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5
Tel: 1-613-562-5800 xt 6830 (Bureau / Office)
                    xt 6839 (Bureau / Office Lab)
                    xt 6836 (IRMS lab)
Téléc. / Fax: 1-613-562-5192
Courriel / E-mail: [log in to unmask]
Toile / Web: www.isotope.uottawa.ca

 

> -----Message d'origine-----
> De : Stable Isotope Geochemistry 
> [mailto:[log in to unmask]] De la part de Shelley Kunasek
> Envoyé : 26 juin 2006 19:14
> À : [log in to unmask]
> Objet : [ISOGEOCHEM] automate LN2 trap?
> 
> I'd like to automate a continuous flow EA/IRMS system to have 
> a liquid nitrogen trap lower into a dewar and then lift out 
> at the right time.  We'd like to basically build this simple 
> component of a precon or a gas bench without having to buy a 
> whole precon or gas bench.  Has anyone had experience 
> building that type of setup?
> 
> Thanks
> 
> Shelley Kunasek
> 
> University of Washington
> Department of Earth and Space Sciences
> 206-543-6223
> [log in to unmask]
>