Best Choice for two columns/one detector

[GCMSNoob]

Anyone have any experience? I'm working with a Bruker GCMS, analyzing gas streams now. Looking to add a liquid injection setup using an available second injector.

So: Dean's switch or just put two columns in and run low flow on the column not in use?

[James_Ball]

We have successfully done the two columns two inlets with a Tee at the end going into a transfer line into the mass spec before. If you have all electronic pressure/flow control it works pretty well. Just set up your methods so they drop the flow on the unused column to around 0.1-0.2ml/min and you should be ok(if you can get by with a head pressure that low). Just have to make sure the combined flows do not overload the pumping capacity of your vacuum system.

[Peter Apps]

The problem with trying to set a low flow on a column going to an MS is that the minimum pressure drop is 1 bar because the end of the column is in a vacuum. If you want to have two columns connected all the time you will need a restrictor through the transfer line, with the columns T-eed onto that.

Peter

[cleh]

Agree with Peter. Another option is to use a six port valve.

[James_Ball]

The problem with trying to set a low flow on a column going to an MS is that the minimum pressure drop is 1 bar because the end of the column is in a vacuum. If you want to have two columns connected all the time you will need a restrictor through the transfer line, with the columns T-eed onto that.

Peter

I think we used a 0.1mm ID transfer line to be the restrictor in the setup I mentioned above. Forgot to mention that. It works similar to the old "no-vent" adapters but you can use a longer piece of transfer line for more restriction if needed.

[Bhavesh Sojitra]

Dear GCMSNoob

I guess you are using Bruker Scion. Please let us know your Experience with Bruker GCMS as compared to Agilent. How is the sensitivity, ease of use, maintanance frequency, after sales service, application support.

We will appreciate your practical experience with Bruker GCMS.

Thanks & Regards

[Mdalmaijer]

I have one Bruker 450/Scion SQ GC/MS which has been excellent. It was an early production model and one board had to be replaced, other than that, I never needed service. Sensitivity, linearity and data acquisition rate is excellent.

Mark

[MSCHemist]

I have the Agilent Quickswap. Both column end in a utilmetal ferrule. I can just switch column 1, column two, and ODP restriction caplillary to the QS in a minute.

[chloesabrina]

Hi MSChemist - what is the agilent quickswap? I am running into problems with 2 capillary columns (one for purge and trap) and the other for SPME/headspace going to one mass spec and huge air leaks. They also have a OPD hooked up so multiple connections and am looking for a better way of doing it to limit my leak issues.

[MSCHemist]

Hi MSChemist - what is the agilent quickswap? I am running into problems with 2 capillary columns (one for purge and trap) and the other for SPME/headspace going to one mass spec and huge air leaks. They also have a OPD hooked up so multiple connections and am looking for a better way of doing it to limit my leak issues.

The Quickswap is an insert that screws onto the end of the transferline and is fed helium from an auxilary EPC at psi. There is a capillary that goes through the transferline that is 100um that provides flow resistance. So at 4psi and 280 deg C and 17cm 100um diameter there is ~ 1.3 ml/min going into the mass spec so you set your column flow less than that or when doing pulses you increase the aux epc pressure as well then set it back down after the pulse.

It was a real nightmare getting the insert/transferline and restriction capillary to make a seal and I have not touched it since. Otherwise it works well. The column screws into it with a nut and stiltite now replaced with Agiltent Utilmetal ferrule. WHen it column is unhooked He spews out the insert at arround 30 ml/min but air does not get into the MSD. It takes less than a minute to change columns from front to back or take one column out and replace it with another (after cooling the inlet).

I think Agilent replaced the quickswap insert with a 2-way splitter with makup.

[MSCHemist]

My current setup also has an ODP. I have the Gerstell ODP 3. I have 2 linlets, a MSD, and the ODP. I have a capillary from the ODP cross piece with a silltite ferrule and a column with the Graphpak for the ODP that I can plug in when someone wants to use it. Otherwise I plug in whatever column I am using.