Chromatography Forum

Does anyone has the hand-on experience in installing 2 columns to 1 MSD simultaneously ? Previously I did install 2 columns using 2-hole ferrule.While I was using one column I would cut down the carrier flow of another to reduce the total flow entering the MS. It was successful in this mean but I got problem in column bleeding from both which significantly increased the background. I am thinking of back flushing by making kinda micro fluidic system on both columns separately. Has anyone been using it now?

Hi Hubert

What you need is a pair of Deans switches, with a narrow bore transfer line to the MS. I doubt that such a thing is available off the shelf, but it might be worth looking around. You could build one from Press-Tight connectros and fused silica.

Peter

Hi Peter,
Long time no see. How are you?
Actually I could use a pair of backflush valves from Agilent for each column to make such configuration. However, I just wonder if it could be simply using a Dean switch or else with one Aux gas to accomplish it. Agilent does has some application note for its Dean Switch for comprehehsive GC but I still can't figure out how to apply it in my case. Peter, do you have any reference that I could look at for that?
Anyway, happy to talk to you again.
Hubert

Hi Hubert

I'm well thanks, still working on the wild dog chemical signalling.

I vaguely recall a paper on a Deans switch interface to a MS, but it might have been to allow switching between an MS and an FID, anyway I cannot find it now .

Backflushing might be the easiest way, as long as you can avoid dead volumes between the columns and the transfer line to the MS. If you can afford to lose a portion of analyte then a single Deans switch could be configured to do the job - you need two switches only if you have to have complete transfer to the MS.

Peter