Once considered a niche technique, ion mobility spectrometry (IMS) has in recent years become an essential tool for resolving molecular complexity. By separating ions based on shape and size, it complements mass spectrometry and other analytical techniques, allowing researchers to distinguish between molecules that would otherwise appear identical.
That said, the technique does not come without its complications. High instrument costs and increasingly complex datasets continue to challenge accessibility and analysis, even as new tools make breakthroughs more achievable. Ion mobility’s potential is clear, but fully harnessing it requires careful planning, collaboration, and continued innovation from analytical scientists.
To get a sense of where ion mobility is headed – and the obstacles still in its path – we spoke with Erin Baker, Associate Professor of Chemistry at UNC Chapel Hill and Director of the CAPTURE Core at the PFAS Superfund Research Center (as well as an esteemed Power List alum), about the field’s trajectory, the technical challenges it presents, and the promising avenues emerging in environmental chemistry.
What key developments, technologies or events that have shaped the evolution of ion mobility in recent years?
I've been able to work with ion mobility since I was an undergrad researcher, back at Montana State University. I've always loved using it, and throughout the years, there've been a lot of exciting innovations within the different components of the instrument. For one, there's been a lot of advancements in electronics and how accurate voltages are delivered to the drift cells or the different electrical components. Throughout the whole development of ion mobility, the ultimate goal that everyone’s been striving towards is higher resolving power; and in the last decade or so, we’ve seen the introduction of a number of promising instruments showing great advances in this area.
As an example, MOBILion's recently new MOBIE system is really pushing the boundaries of what can be achieved within a single serpentine path – and perhaps even through successive iterations of that path. And then there’s Bruker's TIMS–TOF system, which allows you to produce a really high resolving power from a very small unit by slowly releasing ions out of their trapping region. It’s also worth mentioning Waters’ cyclic instrument, which enables ions to be passed repeatedly around the loop – a feature that’s been a big help as well.
It’s also important to recognize the original researchers behind these systems. The cyclic concept, for example, traces back to David Clemmer’s group; trapped ion mobility’s origin is a bit more diffuse; but the MOBILion system grew out of Dick Smith’s lab at PNNL
How are you using IMS?
We really like what we're using ion mobility for at the moment. My group's research focuses on connecting environmental exposures to human health. This includes chemical exposures you might pick up breathing air or drinking water – things you don't necessarily expect you're exposed to.
In particular, we’re interested in capturing a broad swath of the chemicals people encounter in daily life. In this context, ion mobility is a very important tool. With mass spectrometry alone, hundreds of molecules can display the exact same mass. By adding ion mobility, we can also determine the molecule’s shape. It helps narrow down that list so we can be more confident in what we're saying people are being exposed to.
Often, we’ll also couple this with another separation technique, liquid chromatography, for example, to hone in on a specific molecule more effectively. The molecules we’re looking at are primarily those within the body, the blood, or different environmental exposures such as food, air, and water.
What are the main challenges facing ion mobility today?
I think almost everybody in the mass spec field would probably say it relates to the cost of instruments. Although I’m sure more people would love to be able to run these measurements, things can get very pricey, very quickly. Even starting with just mass spec and adding ion mobility later, you’re paying for the spectrometer, the ion mobility, and often the coupling with mass spectrometry, since it’s such a powerful detector. As an alternative, some people run ion mobility with a different detector, such as a Faraday plate. This, however, only provides sizes, not masses, meaning you miss out on an extra layer of information.
I think the new instruments coming out are really exciting, but it often takes a while to decide how to analyze the data in the best way possible. There’s been a lot of work on analyzing the ion mobility dimension, and I think we’re finally at a point where we’re incorporating it more effectively, where before we sometimes had to scale studies down just to process all the data despite it all being of potential value.
What’s your view on the long-term potential of ion mobility over the next 5 to 10 years?
With data analysis more aligned, I hope that we’ll be able to demonstrate the true utility of ion mobility in the next 5 or 10 years. The culmination of this would be to elect it as a specific assay used in an environmental or clinical office, or perhaps even food safety.
In the present, we’re already seeing ion mobility used in areas such as airports – that thing they swab your bags with, they actually put it in an ion mobility instrument! It's set for the size of molecules like TNT and other explosives. However, there are lotions and other things that have molecules of a similar size – which is why it’s so useful to couple with mass spectrometry. In this example, knowing the mass would tell them that it wasn’t TNT, rather something else (a kind of lotion, for example). But all they can do right now is get the size information.
With this in mind, I see no reason why we couldn't see more applications in other areas of research – I think there’s a lot of excitement around it. The use of it in PFAS is just amazing to me – the things we’ve been able to determine using the ion mobility dimension – there’s so much potential!
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