30 Custom GC helps researchers tackle the energy crisis
Despite the versatility of GC systems and columns available off-the-shelf, the GC analysis of permanent gases remains a specialist field requiring a more bespoke approach. We talk to Peter Klawitter, who for over 15 years has been the in-house expert on these custom GC instruments at Shimadzu UK. As well as hearing from him what’s involved in designing these systems, we discover why these bespoke GC systems are proving so useful in the rapidly growing research field of ‘new energy’.
Hello Pete! Can you start by describing what you do in the custom GC group at Shimadzu?
Thanks for the opportunity to talk! In our group, we devise, build and sell bespoke GC systems to the UK market. These are mostly for analysis of commonly-encountered permanent gases such as hydrogen, oxygen, nitrogen, methane, carbon dioxide and carbon monoxide, but we also deal with some of the more obscure gases such as ammonia and nitrous oxide.
We’ve grown substantially since I started at Shimadzu in 2003, and we’ve now got about 70 systems installed in the UK. Many of these are in university labs - and that’s actually where much of our current focus lies in terms of new systems.
Apart from analyte chemistry, what other considerations are there in designing a new system?
A major factor is the analyte level we’re looking at. If the customer just wants to detect at levels of say 0.1% and above, then a thermal conductivity detector (TCD) is usually fine. But even then, we might have to think about the carrier gas, because TCDs can’t distinguish between hydrogen and helium. And of course we need to consider whether the detector might be overloaded by high-abundance compounds, and so require the flow to be split. On the other hand, when the customer needs low detection limits, which is happening quite a lot now especially with our customers in academia, we’ll need a more sensitive detector.
But ultimately, we make our system designs as simple as we can, and deal with the necessary complexity as far as possible through the method. That way, our customers get the best system robustness, performance and flexibility.
When you build the custom GCs, do you start from a standard GC system?
Yes, the core frame for the majority of our builds is the Shimadzu Nexis GC-2030, which is great for custom work because it allows all our additional valving to be fitted on top of the instrument. This frees up the left-hand side of the GC for coupling to an MS detector, which is very handy for applications involving isotope work.
And as for detection, I’ve already mentioned TCD, but there’s also FID for hydrocarbons and ECD for nitrous oxide. Plus of course we have our own patented barrier ionisation detector or BID, which we released back in 2014, and which offers much lower detection limits for the permanent gases.
Shimadzu custom GC expert Peter Klawitter with one of the team’s bespoke instruments for the analysis of permanent gases. Like many such systems, this one is based on a Shimadzu GC-2030.
Why are custom GC systems needed? Isn’t it possible to devise a ‘one-size-fits-all’ solution for gas analysis?
That’s a fair point. Unlike the VOCs and SVOCs analysed by standard GC systems, permanent gases have a much greater variety of physical and chemical characteristics – what we call ‘chemistries’. These really complicate separation and detection, and limit the types of columns we can use. For example, CO2
poisons the commonly used molecular sieve columns, while FID detection won’t work for anything without a hydrocarbon bond in.
Ammonia is a tricky one as well, as it’s pretty aggressive and so needs to be split off into its own detection and analysis line. And in the most challenging situations involving sulphur species, we have to refit the internals of the GC with specially treated alloys to stop the samples ‘sticking’ to the components!
As a result of all this, you typically need multiple columns and detectors for gas analysis, as well as valving to separate out the target species, and carefully-considered valve flows and timings to ensure optimum performance. Essentially, this means that each time a customer comes to us with an application request, we need to create a customised GC system for them.
The custom GC systems designed by the Shimadzu team vary in complexity. This is one of the more intricate designs, involving two valves, three columns, and three detectors.
Example of an analysis conducted using a custom GC system, which in this case uses three sample loops. After backflushing off the C6+
Close-up of the custom GC valving and flowpaths in place on top of the GC, which allows space on the side for an MS detector, if needed.
and H2
are directed to an alumina capillary column, with all the components then detected by FID. Meanwhile, H2
components as one peak, C1
S are separated by Rtx-Q plot, with both separations detected using BID. The final analysis time is just 5.5 minutes. For full details please see Application Data Sheet No. 126.
, O2 , N2 , CH4 and CO are separated on an MS-5A column, while CO2
hydrocarbons , C2
H4 , C2 H6 , C2 –C5 H2
LABMATE UK & IRELAND - SEPTEMBER 2022
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