Using Hydrogen Carrier at a Lower Flow Rate for GC-MS – Separations Compromised?

In the previous ChromaBLOGraphy post, Simple translation of GC methods from helium to hydrogen carrier gas, I demonstrated two Method Translation approaches to switching GC carrier gas from helium (He) to hydrogen (H2) for GC-ECD of organochlorine pesticides.  The first approach involved going from speed-optimized flow (SOF) for He to SOF for H2, which is faster, and that requires a faster GC oven program rate to maintain the same chromatographic elution pattern for the compounds of interest.  The second approach was to start with SOF for He and then just set the holdup time (or linear velocity) for H2 to match that for He.  Yes, we’re below optimum flow now for H2, but an advantage is being able to use exactly the same GC oven program and get essentially the same component retention times as we got with He.

The second approach, that of matching holdup times for He and H2 upon a carrier gas switch, can be used to some advantage with GC-MS where hydrogen is not easily pumped and a higher (optimum) flow would lead to a more drastic detectability loss.  I give examples of both approaches below for GC-MS from the starting point of efficiency-optimized flow for He.  Hopefully you’ll come to the same conclusion I did that running at a sub-optimum flow for H2 carrier did not substantially degrade the separations of example pesticides.

He H2 Different

 

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He H2 Same

4 Responses to “Using Hydrogen Carrier at a Lower Flow Rate for GC-MS – Separations Compromised?”

  1. jaap says:

    nice to see you did this experiment also with MS Jack!! this is very nice for users that are happy with run times and just want to have an alternative from the traditional helium.. great stuff!

  2. Jack Cochran says:

    Thanks Jaap! I have a great Dutch GC mentor who suggested this very experiment! Nice to see it works well, and the new Method Translator/Flow Calculator makes it very easy to set up.

  3. Brendon Parsons says:

    Thanks for running the experiment and writing this up. I was just talking to a professor at a community college last week who was considering switching away from helium for their GCs (including a GC-qMS), and hadn’t even considered hydrogen (unfortunately). After a little discussion about higher optimum flows and method translation, she agreed to give hydrogen a second look. Posts like this help convince people that hydrogen can be a great carrier gas, especially when you make your own!

  4. Trevor says:

    I read a lot of these blogs, and they typically lose me somewhere around the n-oxyl-whatever, but as someone who grew up in production, this one strikes a chord. I can imagine a lot of lab managers who would enjoy a 40% improvement in throughput with similar accuracy of results. And, it’s great to have the option of duplicating the exact same results with a different carrier gas and flow rate change. Flexibility is great to have in a Production or Quality lab! Great info!

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