In this podcast, Director of GLP bioanalysis Lan Li reviews immunoassays versus mass spectrometry-based methods as tools for protein biomarker quantitation. Focusing specifically on mass spectrometry approaches, Lan explores various methodologies, such as top-down, middle-down and bottom-up, as well as the sample preparation procedures required. Lan concludes by reviewing the current challenges impacting protein biomarker quantification and how QPS Holdings, LLC is developing solutions to overcome them.