To assess where the scoring can be further improved, we manually inspected the computed geometries and computed IR spectra for each reference metabolite and compared these with the experimental IR spectra. It appears that about 10% of ions adopt a higher-energy conformational or tautomeric geometry, with a significantly different computed IR spectrum. These higher-energy geometries lie up to 68.8 kJ/mol above the lowest-energy geometry (Figures and). The presence of higher-energy geometries is not uncommon and may be due to inaccuracies in the calculated energies or kinetic trapping of solution-phase conformers or tautomers that are transferred to the gas phase .