GC Carrier Gases – Alternatives to Helium

The helium shortage in the USA doesn’t seem to be getting any better for chromatographers. If your gas supplier is actually able to supply your lab with helium, the costs have probably increased. We (tech service) seem to be getting more calls, however, from customers who are currently not able to purchase helium from their gas supplier, and have no choice but to look for an alternative carrier gas. Please keep in mind, switching GC carrier gases is often not as simple as just swapping out gas cylinders. The phrase “look before you leap” is very relevant when deciding to switch gases, but with appropriate planning, prolonged instrument downtime can be avoided.

Even though we have examples of using nitrogen and/or hydrogen as alternative carrier gases on the Restek website (located in posts throughout the ChromoBLOGraphy and in presentations & articles in our Technical Library), many of our customers are looking for any and all additional information available, no matter what the source. As a result, I decided to take some of this additional information we have discovered in tech service and share it with our blog readers in this post. Their links are presented below.

Please note, since these articles were not written by Restek, we are not capable of controlling their content nor confirming their accuracy, so as with all things found on the internet, consider the source and thoroughly investigate any proposed changes before you implement them. This includes contacting your instrument manufacturer before switching gases.

We found the two below posted on the LCGC website ( www.chromatographyonline.com ).

Hydrogen as a Carrier Gas for GC and GC–MS

This one is from Parker.

Considerations on Switching from Helium to Hydrogen

These two are from Perkin-Elmer.

Nitrogen and Hydrogen as Alternate Carrier Gases for GC/MS

Reducing the Use of Helium in Gas Chromatography

And I decided to include this table from Airgas because I had never seen it before, and found it interesting.

Gas Grade Selection Table for Gas Chromatography (GC)

Hopefully you will find these articles useful if/when you decide to switch carrier gas from helium to another gas. I know we all hope the helium supply situation improves soon, but if not, it may be time to prepare for real possibility that one day the switch will be necessary.

10 Responses to “GC Carrier Gases – Alternatives to Helium”

  1. Travis Weaver says:

    One of the concerns in our lab is volatile analysis, which has a long history of using helium as the purge gas. What happens to this analysis if helium supply is a real problem? How do they perform this in Europe? Apparently EPA is allowing nitrogen purge in draft method 524.4. Here are a few links related to purge and trap:
    http://www.oico.com/Modules/productliteraturepopup.aspx?id=product&productid=36&doccatID=21
    http://www.teledynetekmar.com/resources/app_notes/VOC/Stratum/Nitrogen_Purge_Gas_524.4.asp
    http://www.estanalytical.com/pub/docs/Drinking%20Water%20Analysis%20Conditions%20for%20USEPA%20Method%20524_3%20and%20524_4.pdf

  2. Alan Sensue says:

    Travis:

    Thanks for the links. I’m sure our blog readers will find them useful. Unfortunately, I do not know the most common purge gas used in Europe; I will need to ask around, but maybe one of our readers will know and post the answer. I’m guessing they may not follow EPA methodology, and my understanding is that the majority of their volatiles analysis done using headspace instead of purge & trap, but once again, I would need confirmation from someone more knowledgable in European methodology.

    Alan

  3. The nice part for P&T users is that all of the major manufacturers offer Nitrogen purge applications along with optimized conditions – additionally if you are using nitrogen to purge (in which case you are saving upwards of 440ml of helium per sample) you can set gas saver on since after the first minute the sample has been effectively spit and has focused on the head of the column – of course that is assuming you have an optimized desorb time – Remember to keep your gas saver time slightly longer than the desorb time to assure you have all of your sample on the column. Now for the rest of the world there is a mix of techniques and approaches to volatiles for instance in the UK Purge and trap is common whereas in the rest of Europe headspace is a more common approach to volatiles – Headspace is going to use significantly less gas for operation. Hope this helps, Chris.

  4. James Ball says:

    We have tried using Hydrogen in our volatiles analysis a few times over the years as a carrier gas, but have found it impossible to pass a BFB tune check as it seems there is some chemical ionization going on in the source. I believe it was mass 173 that goes through the roof where it should be almost zero response. If it wasn’t for this we would be using hydrogen carrier and nitrogen purge to reduce our helium usage.

  5. Alan Sensue says:

    Hi James:

    Thank you for reading my post in the Restek blog, and for posting a comment. Other customers have made similar comments over the years, but unfortunately, not much has been written/documented on the subject concerning odd fragmentation patterns when using hydrogen as a carrier gas.

    Alan

  6. Bruce Bornstein says:

    We have been using Nitrogen as a purge gas with good luck. When we tried H2 as a carrier, we were able to meet BFB tune criteria. The problem we ran into is that response for Bromoform dropped by 90%. When we switched back to He as a carrier, the response for Bromoform returned to normal.

  7. James Ball says:

    Alan,

    We have again ventured into the process of switching to Hydrogen carrier for GC/MS and for the volatiles what I am finding is that the problem mass is m/z 96. The tuning requirement for EPA 8260, 624 and 524 require it to fall into the 5-9% versus m/z 95 range, but when using Hydrogen m/z 96 is around 60% compared to m/z 95. This seems to be showing that after 1,4-Bromofluorobenzene looses its Bromine which gives the m/z 95 ion, it is being replaced by a hydrogen. I have tried adjusting the emission current and column flows while maintaining -70eV on the filament but it has no effect. This is on an Agilent 5973 instrument. A recent Thermo webinar showed them getting passing spectra for both BFB for volatiles and DFTPP for semi-volatiles. If I can figure out how to get an Agilent to tune with Hydrogen I will post here again for others benefit, if anyone else has figured it out I hope they will do the same.

  8. Alan Sensue says:

    For those of you who are encountering problems like James and Bruce when trying to use hydrogen as the carrier gas for GC/MS, you may find my most recent post on the subject interesting – It’s a confusing time for GC/MS analysts

  9. Bill Shannon says:

    We are in the process of switching to hydrogen as a carrier gas to do EPA Method 8260B volatiles. Instrument is Agilent 6890N / 5973 inert with a high efficiency turbo pump. We see a large increase in BFB 99/95 ratio presumably because of hydrogenation of the 95 fragment otherwise BFB tuning is fine. Aromatic and branched hydrocarbon recoveries are excellent. Our principal problem is very large attenuation of most halogenated compounds. Particularly if the hydrocarbon component has undersaturated bonds. For example Tetrachloroethane abundances and recoveries are relatively unaffected but Tetrachloroethene is abundances are down to 20% of recoveries when using helium as the carrier gas. We are using 200C for the source temperature and auxiliary heater. Transfer line temperature is 120C and GC inlet temperature is 150C. We are using a Vocarb 3000 K trap and got some improvement in recovery by lowering desorption temperature from 250C to 220C. I should add… The 5973 has the appropriate focusing magnet and we are using the recommended 6mm draw out plate.

  10. Alan Sensue says:

    Hi Bill:

    Unfortunately I don’t have an answer to what you are experiencing, so I asked a few others to review your comment. If they have any ideas, I’m sure they will post a reply. Thanks for reading my post.

    Alan

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