Saving helium on a 5890

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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I'm running a HP 5890 series II plus and I'd like to cut my helium consumption. I have a "gas saver" which I have yet to install. It has a simple mechanical toggle with a metered orifice that reduces flow to some minimum amount overnight, but I'd like to do something automatically after a run completes.

This problem has me pondering the best strategy, and I'm wondering if there is some way to automatically shut off split flow a few minutes into the run, once all the sample is on column. Has anyone heard of such a technique? I think this sort of thing is now standard on modern GCs.
If the 5890 has Electronic Pressure Control for the inlet it should allow you to set split flow from the computer. If it still has the needle valve flow control then it won't be possible.

If it is full EPC then you can always make a standby method with low column and split flows. Then you just load that method into Chemstation before running a sequence(at least you can if you use MSDChemstation, not sure about the other one) and it will load the standby method once the sequence is finished.
The past is there to guide us into the future, not to dwell in.
Yes, you are right, but I only have the needle valve flow control. I might be able to salvage the components from another 5890 and upgrade, but I had heard that the electronic flow control is not very reliable. What do you think?
James_Ball wrote:
If the 5890 has Electronic Pressure Control for the inlet it should allow you to set split flow from the computer. If it still has the needle valve flow control then it won't be possible.

If it is full EPC then you can always make a standby method with low column and split flows. Then you just load that method into Chemstation before running a sequence(at least you can if you use MSDChemstation, not sure about the other one) and it will load the standby method once the sequence is finished.


See above. Either make and load a "low flow" Method and have that load on last line of the Sequence, or the software should have a gas saver function that you can incorporate except when you need the higher flow at the beginning of the injection.

Of course another way to cut helium use is to eliminate it and use a hydrogen generator and hydrogen carrier gas.

I've had no issues with Agilent flow control since back in the 5830/5840 days.
jkloepping wrote:
Yes, you are right, but I only have the needle valve flow control. I might be able to salvage the components from another 5890 and upgrade, but I had heard that the electronic flow control is not very reliable. What do you think?


We had some trouble with the first gen EPC on 5890 when using methylene chloride solvent. The o-ring inside the solenoid would degrade and need to be replaced about once a year. The later models must have used different material since they were much more reliable.
The past is there to guide us into the future, not to dwell in.
The split ratio is set by turning the manual mass flow controller until the total flow coming out of the split vent is the right multiple of the column flow controlled by the EPC. I just keep mine 1 ml/min and 10:1 split so total flow is 10ml/min.
You actually raise two issues. The first is gas saver for a high split, the second is switching away from helium while in idle.

For the first, the 5890 creates an interesting challenge. The split flow is a result of the total flow less the column back pressure. So... the only way you can invoke a high split is to invoke a high total flow. I have done this with a three way valve and two total flow controllers but did not test it too extensively. The challenge is to do this with an autosampler....... and you have to have sufficient separation to get away from flow perturbation.

For the second, you can switch to nitrogen while in idle if you wanted to. Three way valve to two gas streams. Best to use normally off mode for the idle time if you don't run a huge number of samples. This I have done on several instruments for a customer of mine. I also presented a poster on it at Pittcon.

Best regards,

AICMM
The flow problem came up recently when I switched back to helium from a hydrogen generator. I did that because I was having problems getting good matches in my existing library using hydrogen. I have a three way valve installed, so I can manually switch to hydrogen overnight, but sometimes I like to start an analysis before I leave, and I cannot switch a manual valve in that case.

What would be ideal I think, would be an electronic three way valve that would be actuated automatically after the run.
You can kick your run into splitless mode a few minutes into the run; it will use a lot less He. Just make sure you give your solvent peak time to clear the injector port.

At the end of a batch load and execute a method that is splitless only. You'll sit in idle that way running just the column flow.

A tank of He lasts us several months using these methods.
Mark Krause
Laboratory Director
Krause Analytical
Austin, TX USA
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