A mass spectrometer is a sensitive and specific instrument." In some form or another, this is often the label applied to the platform by all manner of professions (chemists, physicists, biologists, physicians, clinicians, and laboratorians, novice and expert alike). This is a view of mass spectrometry (MS) through rose-colored glasses. It should be properly said that MS can be sensitive and specific, but not without due consideration for the measurement to be performed. In clinical laboratories, this measurement is the extraction, detection, and often, quantification of a compound of interest from a biological matrix.