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Techniques & Tools Gas Chromatography

Your Shortcut to Fast GC

sponsored by Avantor, Leco, Peak Scientific and Shimadzu

Do you feel the need for speed, but don’t have the right kit or know how? We understand – and that’s why we brought together four leading experts and technology providers to help you jump-start your fast-GC journey towards increased throughput, productivity, and cost effectiveness. 

Of course, we’d urge you to watch the recording of the live event, when time permits: view here – but we know you’re in a rush; that’s why you’re here. To help you shift up a couple of gears to fast GC in just a few minutes, we present this shortcut guide.

Fast GC – why you should care

Tony Edge, Site Director (Production & R&D) Hichrom, Avantor, offered a brief history, walked us through a theoretical 101 (prepare for the Purnell equation and the importance of phase ratio), and explored some practical implications: 

  • Injection volume – the available surface area has reduced, so the column has less capacity; therefore, injection should be reduced (or split ratio should be increased).
  • Film thickness – increased film thickness results in reduced column efficiency; therefore, thin film thicknesses must be used.
  • Column length – can be reduced to cut down run times.
  • Gas flow rate – though the linear velocity increases, the volumetric flow rate is not altered as much.
  • Dispersion issues – greater care should be taken when installing columns.

Tony also highlighted the advantages of 3–10 x increase in speed while retaining resolution using several applications, including chamomile analysis, rapid separation of fragrance allergens, and pesticide analysis.

Getting fast on your own supply

Ed Connor, Product Manager, PEAK Scientific, talked about the need for a safe and secure supply of hydrogen as a key step towards fast GC, and elaborated on the benefits of gas generators in this regard:

  • Convenience – gas on-demand, with no need to worry about cylinder changes or stock control.
  • Consistency – in both quality (no impurities) and supply (gas generators don’t run out…)
  • Safety – one less pressurized cylinder in your lab
  • Green – energy efficient with no need for repeat deliveries
  • Economic – more easily managed life-time running costs

Fast GC, meet rapid detection

Franz Kramp, Product Manager GC, Shimadzu Europa, shared insight into method optimization needed to shift gears to fast GC, exploring in detail – with pros and cons:

  • Increasing initial temperature
  • Increasing the gradient of the temperature program
  • Increasing the linear velocity of helium carrier gas
  • Switching to hydrogen carrier gas

Franz also offered tips for adjusting your fast-responding GC detector for sharper peaks by altering two parameters: i) sampling frequency and ii) noise filter settings.

Fast GC in the wild

David Benanou, Expert Analytical Research, Veolia France, dug into the applicability of fast GC and the need for sensitive, robust, high performance fast MS systems – particularly in (waste, treated, and environmental) water analysis. Crucially, David told us that the transfer to fast GC using hydrogen carrier gas is not only possible but even easy,  providing some more points for consideration:

  • Cost savings can be achieved by switching from helium to hydrogen – and safety concerns over the latter can be handled easily.
  • For successful chromatographic method transfer, follow a systematic calculation approach
  • Analytical throughput can be improved significantly via reduced run times with excellent resolution.
  • Appropriate instrumentation is important for sensitivity, high-quality data, and comparable MS spectral fragmentation for identification purposes. 

Finally, fast Q&A

As with most discussion forums, the live question and answer session with the audience proved to be both informative and entertaining – here are the highlights:

Great to hear about the benefits, but... What are the biggest challenges associated with the use of fast GC?

Tony Edge: Fast GC is an incredible technique, as I’ve said, but unfortunately it amplifies any minor issues we may have within the system. As with all forms of ultra fast performance – whether it be a fast car or fast chromatography – minor components (for example, connectors) that wouldn’t typically have a major impact on performance at “normal” speed suddenly become critical. Dispersion is a big issue, hot spots in the column can also cause issues.. And – as I explained – we must pay attention to sample loading. And yet, though there are some challenges (all of which can be tackled with the right equipment), the benefits are huge. 

David Benanou: One thing we’ve not covered is the sudden ramp up in data acquisition – so be prepared!

What requirements must a GC fulfil for “fast” operation?

Franz Kramp: I covered off many of the parameters – in particular, the need for rapid heating – but we also need to think about the cooling speed, which also needs to be rapid, otherwise gains are lost. But please note that rapid cooling can have implications on column choice. Elsewhere, reduced inner column diameters result in increased pressure – so the GC must be capable of operating at pressures over 700 kPa. Finally, sharp peaks require rapid detection! 

Tony Edge: Franz is right. It’s not just about getting one component right – it’s about getting the right mix.

What’s the best carrier gas?

Tony Edge: If I was being controversial, I’d say nitrogen. But no – it’s obviously hydrogen. Of course, there are safety implications of having cylinders of flammable gas, but I’m sure Ed has got something to add… 

Ed Connor: I would tend to agree that it’s hydrogen. And, yes, there are clear advantages to using a gas generator – not least safety.

David Benanou: I’d add that, with the right equipment, the move to hydrogen generators can actually save money.

How long does it take to convert from helium to hydrogen?

Ed Connor: I would say that it depends how well you’ve prepared; if you’ve not fully considered all the factors that come into play, you may lose time. It will also depend on the detector type, where hardware changes may be required. The question is a little like asking how long is a piece of string – but, in short, it can take anywhere from a couple of hours to a couple of days; for example, if you’re waiting for the MS background to settle.

Franz Kramp: On the GC side it’s no problem. Even using the same parameters – just indicating that hydrogen is connected – you’ll get similar results. But then a whole world of optimization opens up!

Do you see any limitation to reduction of the column inner diameter and thus how fast GC can go?

Tony Edge: I think this is potentially one of the exciting areas we could move into. We’ve seen – in the research community – the etching of GC capillaries for some time now. That said, there is of course a limit at some point. And I’ve already covered what challenges we would face in that pursuit. However, I do feel we should be working towards IDs of 1 or 2 microns – or maybe even into the nanometer range – and I think such columns are not so far away.

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