Chromatography Forum

Hi ,

What is the typical carrier gas is set up for GC in your lab?

Helium ,,nitrogen and Hydrogen? all 3 ? or 2 ?or 1?

Pros n cons with this?

Helium, Pro , safe, con expensive
Hydrogen Pro best carrier gas, con "risk factor" Get a generator
Nitrogen Pro cheaper than helium con not the best carrier gas , longer run times
Argon Specialist applications only

We are trying to go with hydrogen unless the ASTM method requires helium. Faster chromatograms and better chromatography with hydrogen. Hydrogen isn't as scary as people make it out to be though - http://www.restek.com/Technical-Resourc ... orial_A016

We have the new Agilent Hydrogen Sensor in a 7890B and it works well. So far only set it off once. http://www.chem.agilent.com/en-US/produ ... ensor.aspx

We are trying to go with hydrogen unless the ASTM method requires helium.

Don't hold your breath waiting for "official methods" to include hydrogen carrier. I'd suggest you document equivalent results both ways, run supporting precision and accuracy as agreed upon with your QA folks.

I have two GC's a GC/MS with 2 inlets and a 5890 SII with one inlet and an FID. I use helium for both. For GC/MS I rely heavily on library matches for identification and hydrogen tends to cause masses to shift +1. It already has a heck of a time telling the C15H24 terpenes apart and several other isomeric compounds as well.

The 5890 I considered going with hydrogen but I inject a lot of chlorinated solvents and worry about HCl gas generation and it would be a pain to plumb the septa purge and split vents to the hood exhaust. Nitrogen is also a possibility but that doubles run times. I keep the 5890 always at 10:1 split so a 15 ml/min helium flow and shut it down when not in use.

I use nitrogen for all makeup and vial pressurizations headspace loop sweeps.

I go through about 1 helium cylinder every 3-4 months.

We are trying to go with hydrogen unless the ASTM method requires helium.

Don't hold your breath waiting for "official methods" to include hydrogen carrier. I'd suggest you document equivalent results both ways, run supporting precision and accuracy as agreed upon with your QA folks.

way ahead of you

Went from helium to hydrogen and have saved tons of money

Here's a link to an LCGC ChromAcademy webinar on Fast GC - cut your analysis time by using hydrogen as a carrier gas.

http://www.chromatographyonline.com/fas ... lysis-time

What is the general consensus on hydrogen supplied from a gas generator vs cylinders?

Do a search, this has been discussed a few times before

What is the general consensus on hydrogen supplied from a gas generator vs cylinders?

There was a discussion about the pros and cons of both gas sources here.

viewtopic.php?f=2&t=26210

The 5890 I considered going with hydrogen but I inject a lot of chlorinated solvents and worry about HCl gas generation and it would be a pain to plumb the septa purge and split vents to the hood exhaust.

Chlorinated solvents + hydrogen + heat = HCl + potential inlet damage
One lab I know of destroyed an Agilent (6890) inlet trying out hydrogen as a carrier gas with DCM as an injection solvent. Your inlet conditions may vary, but proceed with caution.

The 5890 I considered going with hydrogen but I inject a lot of chlorinated solvents and worry about HCl gas generation and it would be a pain to plumb the septa purge and split vents to the hood exhaust.

Chlorinated solvents + hydrogen + heat = HCl + potential inlet damage
One lab I know of destroyed an Agilent (6890) inlet trying out hydrogen as a carrier gas with DCM as an injection solvent. Your inlet conditions may vary, but proceed with caution.

Never mind the inlet, it cannot be good for the column either !. Do you have any more information on this please ?, I rarely use dichloromethane, but I do need my columns to be in tip top condition.

Peter

I routinely use DCM and hydrogen carrier - I cannot say I have noticed any greater inlet or column damage. The analytes are pretty forgiving though, just hydrocarbons.

I have moved inlet shells from this instrument to others that handle active analytes - still no issues that I have noticed. I do ensure the inlets are maintained with at least 20 cc/min of flow at all times, so perhaps that alleviates the potential damage.

Both Agilent and Thermo have Webinars on hydrogen as a carrier gas where GC/MS is at least mentioned. Both recomend not using chlorinated solvents but the problems with reactivity seem to vary with inlet type and conditions. One lab I know of reported a damaged inlet, another had no problems with inlet or column damage but lost some target analytes. They were both trying method 8270 targets with hydrogen.