The structural elucidation
of metabolite molecules is important
in many branches of the life sciences. However, the isomeric and isobaric
complexity of metabolites makes their identification extremely challenging,
and analytical standards are often required to confirm the presence
of a particular compound in a sample. We present here an approach
to overcome these challenges using high-resolution ion mobility spectrometry
in combination with cryogenic vibrational spectroscopy for the rapid
separation and identification of metabolite isomers and isobars. Ion
mobility can separate isomeric metabolites in tens of milliseconds,
and cryogenic IR spectroscopy provides highly structured IR fingerprints
for unambiguous molecular identification. Moreover, our approach allows
one to identify metabolite isomers automatically by comparing their
IR fingerprints with those previously recorded in a database, obviating
the need for a recurrent introduction of analytical standards. We
demonstrate the principle of this approach by constructing a database
composed of IR fingerprints of eight isomeric/isobaric metabolites
and use it for the identification of these isomers present in mixtures.
Moreover, we show how our fast IR fingerprinting technology allows
to probe the IR fingerprints of molecules within just a few seconds
as they elute from an LC column. This approach has the potential to
greatly improve metabolomics workflows in terms of accuracy, speed,
and cost.