The Metabolite Profiling Core Facility houses two liquid chromatography / mass spectrometry (LC/MS) systems. The mass spectrometers are Thermo Scientific QExactive Orbitrap instruments, which are capable of measuring mass-to-charge ratios with less than 5 ppm error and a resolution of up to 140,000 and can also collect MS/MS fragmentation data. Each mass spectrometer is coupled to a Dionex UltiMate 3000 ultra-high performance liquid chromatography (UPLC) system designed for pressures up to 1000 bar, permitting rapid separation times of ~30 minutes per sample. Together with a library of several hundred synthetic standards, the combination of exact mass, fragmentation, and chromatographic retention time data permits the positive identification of most common cellular metabolites. Operating the mass spectrometers in either targeted or full-scan mode enables both hypothesis-driven and hypothesis-generating (untargeted) experiments to be performed.