Interest in ion mobility mass spectrometry (IMS) technology is growing rapidly. The signs are everywhere. Since the year 2000, the number of abstracts submitted to ASMS mentioning ion mobility has grown more than 10-fold – from 30 to more than 350 in 2015. For most of that time, ion mobility has been available commercially in high-end research instruments or in homemade platforms.
Waters changed that with the introduction of the Vion IMS QTof mass spectrometer. With ion mobility now available in a benchtop system, IMS is routinely accessible for more scientists. And it’s finding applications as diverse as pesticide screening, food safety, natural product analysis drug development, petroleomics, and metabolomics .
What’s behind the interest? Separations power and throughput.
As a gas-phase separations technique, ion mobility can give you information about a molecular ion’s mass, charge, and shape [or average rotational collisional cross section (CCS)], an important distinguishing characteristic of an ion related to its chemical structure and three-dimensional conformation. Unlike chromatographic retention times, CCS values are not in any way affected by matrix or mobile phase composition. Measuring this additional characteristic reduces false positives and false negatives adding more confidence to screening applications.
Ion mobility gives an extra dimension of separation resulting in a higher peak capacity (number of resolved peaks per unit of time). This helps when separating co-eluting structurally-similar compounds such as isomers and conformers which can have different physicochemical characteristics such as toxicity and taste.
When Severine Goscinny of the Belgium Scientific Institute for Public Health speaks about ion mobility, you can hear the excitement in her voice. One application for her use of ion mobility mass spectrometry is with steviol glycosides, a sweetener derived from the leaves of the South American plant Stevia rebaudiana. They’re an attractive sugar substitute because of their natural origin and for diabetics and others on a carbohydrate-controlled diet, they do not induce a glycemic response when ingested. As such, they are found in many food products.
The European Food Safety Authority (EFSA) is requiring food product manufacturers to provide more data for the steviol glucosides in their food products and measure them in steviol equivalents rather than absolute concentrations. Problem is, these glycosides, and there are seventeen EU recognized steviol glycosides, often co-elute and fragment in a way that makes it very difficult to tell them apart by measuring their nominal mass alone.
“If you don’t know which is which, or if it’s a fragment from another steviol glycoside that is co-eluting with the targeted steviol glycoside that you’re quantifying, then your results are biased,” Dr. Goscinny says. “With ion mobility and today’s software, we can easily and quickly separate these compounds even if they co-elute, even if they are isobaric, and precisely profile what is in the food. Before ion mobility came along you couldn’t do that. It’s a very powerful technology and a powerful way of giving you confidence in your results.”
Waters Vion IMS QTof mass spectrometer is making its Pittcon debut this year. See for yourself what all the excitement is about.