We also showed that IRIS on an MS n -enabled platform can aid in linking phase I with phase II metabolites, thus revealing the metabolic pathways. An ion trap mass spectrometer in combination with a tunable IR laser allows us to record an IR spectrum of the glucuronide aglycone generated via CID MS/MS. Matching with IR spectra of observed phase I metabolites establishes a direct link between the phase II and phase I metabolites. IR spectra give direct information on the functional groups of a metabolite as well. We demonstrate the added benefit of this in practice by identifying several metabolites resulting from MDZ hydrolysis in an acidic environment. Here, the IR band corresponding to an ketone induced by MDZ ring-opening directly pointed towards a likely candidate structure.