Analytical methods using hydrogen/deuterium exchange are provided which reduce or eliminate the back-exchange of deuterium for hydrogen. The methods, which are useful in protein and peptide mapping, include the steps of (a) providing a peptide or protein comprising a solvent accessible hydrogen; (b) exchanging the solvent accessible hydrogen for a deuterium; (c) separating the peptide or protein with supercritical fluid chromatography; and (d) analyzing by mass spectrometry the mass of the separated peptide or protein. Supercritical fluid chromatography enables the observation of fast exchanging hydrogen atoms missed using conventional liquid chromatography methods.