Multibed or single bed traps for GC-MS?

[lespaul]

Hi everyone, Im setting up the gas lines for our GC-MS using He as carrier.

Im wondering if I should go with a multibed filter - that is, one that scrubs for O2, H2O and HC - or go with 3 separate single bed He filters?

Here is one sold by Restek - http://www.restek.com/catalog/view/981/22600 - by VICI. They recommend installing a indicating O2 filter downstream to help monitor the gas quality.

Another popular one I've seen was the Agilent Big Universal trap, though not sure if its a multibed or not:

http://www.agilent.com/cs/library/userm ... 029108.pdf

Any thoughts on this would be appreciated.

[Peter Apps]

My preference is for a single unit - then you have fewer connections that can leak.

I have used the VICIs from Restek, no complaints.

Peter

[tkubowicz]

Hello

I've been using Agilent BUT for years (with GCMSD) and they are really good. Don't have expirience with Restek though.
I think that one thing to remember is that no matter what trap you're using it should be installed vertically and gas should flow from bottom to top (I've seen that people don't care about it) - it has impact on efficiency plus lifetime.

Regards

Tomasz Kubowicz

[Peter Apps]

I think that one thing to remember is that no matter what trap you're using it should be installed vertically and gas should flow from bottom to top .

A very important point.

Peter

[dblux_]

I think that one thing to remember is that no matter what trap you're using it should be installed vertically and gas should flow from bottom to top .

A very important point.

Peter

Yep, but gas flow should be from top to bottom of the trap.

[James_Ball]

I think that one thing to remember is that no matter what trap you're using it should be installed vertically and gas should flow from bottom to top .

A very important point.

Peter

Yep, but gas flow should be from top to bottom of the trap.

Most of the manufacturers show it from bottom to top, at least on the ones we get. I have used both the Agilent BUT and the Restek, along with three separate ones, all perform the same to me. The single multibed trap though I like better since it requires less connections. I usually also put an indicating O2 trap at close to the instrument as I can, it will catch any O2 if the trap becomes saturated and will indicate if you have any leaks. Best if it is placed so you see it every day.

I always did flow from bottom to top just like I would on an HPLC column, flow against gravity reduces the chance packing will get compressed, though it really shouldn't matter. Most important is vertical not horizontal since horizontal can lead to channeling if the packing settles away from the side of the trap.

[dblux_]

... I always did flow from bottom to top just like I would on an HPLC column, flow against gravity reduces the chance packing will get compressed, though it really shouldn't matter...

James, do you really care for HPLC column orientation ?
If I had to install HPLC column vertically, I would have to put Dionex thermostatted column compartment on it's side

Orientation of the label on trap body suggests inlet joint on the top of Agilent BUT.
http://files1.kyozou.com/Picture.aspx?w ... d=28693165
Otherwise making notes on the label would be inconvenient. Esthetic reasons neglected

[James_Ball]

... I always did flow from bottom to top just like I would on an HPLC column, flow against gravity reduces the chance packing will get compressed, though it really shouldn't matter...

James, do you really care for HPLC column orientation ?
If I had to install HPLC column vertically, I would have to put Dionex thermostatted column compartment on it's side

Orientation of the label on trap body suggests inlet joint on the top of Agilent BUT.
http://files1.kyozou.com/Picture.aspx?w ... d=28693165
Otherwise making notes on the label would be inconvenient. Esthetic reasons neglected

I always preferred HPLC columns vertical, but even our Agilents put them horizontal. I guess I learned too well from my Analytical Chemistry Professor 30 years ago

I do remember one trap that had a flow arrow and a top label but all of the rest of the label was printed upside down if you installed it as it indicated.

I have been spoiled since going to gas generators though, you really don't need the traps and they rarely go bad after they are installed.

[RogerBardsley]

If you are scanning below 40 (Argon MW) get a trap that is packed in helium. It takes a while for the argon to purge out.