Identification and quantitation of drug metabolites is an essential part of the drug discovery process. High sensitivity and high mass accuracy analysis is required to detect and identify low levels of potentially undesirable metabolites. High levels of chemical background and matrix effects interfere with the ability of mass spectrometer s to detect and characterize metabolites. Conventional LC flow rate instruments may be unable to detect minor metabolites due to the lack of sensitivity. Although nanoflow ESI helps to enhance the signal, the analytical time becomes longer and robustness is challenging. In this work, we demonstrate the ability of a micro-flow LC-ESI system with a high performance Q-TOF to detect low levels of drug metabolites.