Severe spectral broadening observed in some IRIS spectra can limit the performance of our method. Extensive broadening is often caused by strong ionic hydrogen bonds that induce shared-proton motifs 50-53 . Such problematic spectra may be avoided by selecting different adducts. For instance, for Laspartic acid (HMDB0000191), the [M-H] -ion shows severe broadening , while both [M+H] + and [M+Na] + ions do not (Figure ) . We also note that spectral broadening in such systems is often reduced on cryogenic tandem mass spectrometry platforms . Alternatively, IRIS identification may be applied to MS/MS fragments, which typically exhibit better resolved spectra , in combination with a bottom-up approach for structure elucidation. This also extends the applicability of the IR spectral library towards molecules beyond its upper mass limit .