Using Hydrogen as carrier and make up gas

[dlntx9]

Recently I came across a 5890 setup that was using Hydrogen as the make up and carrier gas. Does anyone have any experience with this setup? Currently I am using hydrogen, helium, and air. I like the idea of switching from tanks to just a hydrogen generator, and an air generator. What would be the possible drawbacks if I were to do this?

[Steve Reimer]

Agilent has a presentation on alternate carrier gasses at http://www.chem.agilent.com/Library/sli ... drogen.pdf

Much of it is directed to nitrogen but it does list some of the advantages of hydrogen.

[AICMM]

dlntx9,

Flammability. Otherwise, not much. Remember your split vent flow (and column flow/makeup with the flame turned off) are venting into your facility. If you have good ventilation (especially at the roof) this should not really be an issue. Or plumb the split vent to a hood.

Remember as well that whatever H2 you add via make-up you should subtract from the H2 flow to the detector since you only want a total flow of H2 between 25 - 40 mL/min or so.

Best regards,

AICMM

[Consumer Products Guy]

We have started a switch to hydrogen as carrier gas, works fine; but with that we changed the make up gas from helium to nitrogen. Hydrogen is not typically used as a make-up gas, that would make the flame richer than normally used, wouldn't it?

[aidnai]

Hi Dustin,
We have looked into this as well, especially as helium prices continue to rise. The upfront investment in a hydrogen generator is the only thing keeping me from going that route at the moment. In the interim I am continuing to use helium, but lower grade with a purifier. If/when I do decide to go Hydrogen, I will probably start with bottles until I'm comfortable with the method changes needed, then finally go for the generator.

[MSCHemist]

The total hydrogen should be 35-40 ml/min and the air ~400 ml/min. I'm not sure using the hydrogen as a simultaneous fuel and makeup would affect the FID. Nitrogen may be better at drawing analytes from the column exit into the flame so the sensitivity may decrease with the referred setup.

[Peter Apps]

Hydrogen is a very good carrier gas.

If you use hydrogen as make-up it follows exactly the same path as the hydrogen fuel gas - up inside the jet assembly, past the column tip and out of the jet. Total hydrogen flow should be the recommended fuel gas flow. You might see a minor loss in sensitivity compared to nitrogen as make-up, but very little difference from helium as make-up. This is because the mechanism of ion formation in the flame works better if there is a zone of hydrogen mixed with an inert gas below the combustion zone.

Peter

[dlntx9]

Thanks to everyone for all the replies. This is how I'm thinking the setup would be.

I would have a hydrogen generator, and an air generator. the air generator would run straight to the 5890 with a regulator between the generator and 5890.

From the hydrogen tank I would attach a "y"type connector. from the "y" I would run a line into the carrier gas inlet on the 5890 and from the other side of the y I would run a line into the make up gas inlet. I will install separate regulators for the carrier line and the make up line past the "y" split about a foot before the lines attach to the gc.

[Peter Apps]

There is no point in running hydrogen as a makeup gas (see my previous post). Just cap off the make-up gas inlet.

Peter