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International audience; The gas phase IR spectra of α2,3 and α2,6 linkage isomers of sialic acid-containing human milk oligosaccharides and N-glycans epitopes are measured in the 3 µm spectral range using IRMPD spectroscopy in protonated and Na+ charge states. Each linkage isomer has a unique IRMPD fingerprint, providing a convenient diagnostic of the sialic acid position. Finally, a generic trend is observed: 3-linked sialic acid results in a significant broadening of the spectroscopic signature regardless of the glycan core and the charge state which suggests a drastic influence of the sialic acid position on the glycan conformation.

An original workflow allowing inline FAIMS separation, electrospray ionization, mass analysis and ion spectroscopy (IRMPD: InfraRed Multiple Photon Dissociation) is presented for multidimensional molecular analysis. This new instrument consists of an ultraFAIMS (Owlstone) device interfaced to a linear ion trap (LTQ XL Thermo Scientific) which was modified for IRMPD spectroscopy. Two modes of operation are demonstrated on an isomeric mixture of paracetamol and 2-phenylglycine. In the first mode a FAIMS (high-Field Asymmetric waveform Ion Mobility Spectrometry) separation of the isomers is performed with a static compensation field for mass- and isomer- selective ion spectroscopy. In the second mode, the compensation field is scanned while the ions are irradiated at a fixed wavenumber. The advantages of this workflow as compared to traditional FAIMS-MS and IRMPD spectroscopy are described. The potential of the two modes for molecular spectroscopy and analytical applications, in particular the new “omics” are discussed.