Chromatography Forum

I put on a Y splitter to send my column effluent to both MS and FID. I'm wondering if this is going to work?
Cuz the MS is at 15 psi lower than the FID is all of the effluent going to the MS? Can I put a restrictor between
the effluent and the MS to try to balance flow?

A Y- splitter on its own will not work - the MS vacuum will not only take all of the column flow but will suck gas from the FID. You can try with a restrictor but because gas viscosity changes with temperature you will not get a constant split ratio between FID and MS during a temperature programmed run.

There have been some threads on this - have a look in the archives.

Peter

You can use a Deans splitter which, for example, keeps the column tail at 4psig - hence also needs plumbing in to the EPC/pneumatics.

Maybe if you used a 60m 0.18ID column for the MS and a 30m 0.32ID column for the FID you could somewhat balance the flows.

Another option is to install a second injection port and do a dual injection, that would probably be the easiest route to take. If it is an Agilent you can do that running a staggered injection sequence and the software should automatically link the first run on one detector with the second run on the other so that it displays the chromatograms together, or they can be unlinked if you wish.

Using different diameter capillaries at the end of the column is the starting place. The trick is handling this in a way that you can ramp the oven temperature without signifiant effect on the split ratio between detectors. It is that changing gas viscocity that Peter mentioned. I've seen this done - even with a split between three detectors, but it has been years and I don't remember the trick to it. (I thought it was pretty slick when I saw it...)