Multiple Detector GC-MS

[degenste]

I will be purchasing a GC-MS which will be a 5972msd connected to either a 5890 II+ or a 6890N GC. It is rather critical for me to be able to collect MSD data while at the same time collecting TCD (and if possible FID) data. (Quantification of Hydrogen is very important.)

I have been looking around and it seems that MSD Chemstation G1701CA or G1701DA are the ideal softwares for doing this. For example G1701CA supports 5890 and 6890's, 5972 MSD and the TCD and FID.

In my ideal situation I would basically have all three detectors collecting data from the exit of one column and then would display and log the data from all three detectors simultaneously. The effluent would be split with some of it going to the MSD and the rest going to the TCD and FID in series.

From what I have seen this should be possible after writing some macros. Is this correct? Can anyone tell me if this is possible and point me in the right direction if it is? Please?


Thanks

Nick

[Peter Apps]

Bear in mid that if you just split the effluent from the column to the three different detectors the vacuum in the MS will suck gas the wrong way down the lines to the FID and TCD. You need to have appropriate restrictors, and maybe some make-up gas at the split point.

Peter

[AICMM]

Chemstation is supposed to be able to do both MS and GC detector channel. I worked with a group that was planning to do just that before they ran out of money. I would suggest calling Agilent to chat with them about that since they will be happy to sell you the software.

On a different note... I agree with Peter that you need to be aware of the flow restrictions that you face with the MS. You want to make sure you limit the flow into the MS (generally I have found less than a mL/minute.) Second, I would point out that if you want to do hydrogen on the TCD (assuming it is not really high levels) you have ruled out helium as a carrier since their thermal conductivities are near each other. If they are high level, I hear that TCD's will behave strangely (not actually done it) doing high level hydrgogen. You also, obiously, have ruled out hydrogen as a carrier.... So I guess I am wondering what carrier you would use for the GC?? You might be better off splitting at the front and using two columns or just doing two injections on two completely separate channels.

[degenste]

Thanks for the reply Peter

I am pretty sure that the TCD and FID can be hooked up in series. So I would only have to split once to divert a small portion of the effluent to the MSD and the bulk of the gas would go to the TCD/FID.

At this point my main concern is not with this splitting issue, but with regards to the software. Will the software allow me to simultaneously collect data from the MSD and TCD at the same time? I must quantify Hydrogen however the normal 5972 MSD does not collect data at m/z = 2.

Peter, if you or anyone else have any info on this specific software issue or on whether it is possible, please let me know.

Thanks

Nick

[CE Instruments]

Whilst it may be possible to run a GC with the column split to TCD/FID and MS I would advise against it. Getting the split to work well is difficult and the extra plumbing will add lots more possible sources of leaks. Use your GC/MS as it should be for MS work and buy a cheap GC/TCD/FID and run it to a dedicated data system. This way you can optimise both systems properly and greatly increase your reliability.

[degenste]

Thanks for all the input.

I will be buying a used system because I don't have funding to purchase a new GC/MS from Agilent. I will also be getting an older version of MSD Chemstation from the used equipment dealer (probably G1701CA). I have tried to speak with agilent about this, however they haven't been any help because they don't support their older software of hardware products.

I am not concerned about the hydrogen TCD analysis issue because we have 5 other agilent GC's in our lab set up to analyze hydrogen of which I am very familiar.

Using a dual column setup and 2 separate detectors (TCD and MSD) is defintitely a possibility if the split will be unreliable.

My purpose for using a GC/MS is to use the quantification (especially H2) ability that I am familiar with (GC functionality) however I will be starting to analyze and identify unknown compounds in the effluent from a reactor for which I would like the MS functionality.

Can anyone point me in the direction of any information on splitting column flow for MSD detection?

Thanks again

Nick