The present invention is generally related to the separation, fractionation, and/or characterization of molecules and/or biomolecules in one or more mixtures. After fractionation, different phases of a partitioning system can be analyzed via an analytical technique such as spectral analysis, chromatography, or the like, to produce a spectrum or other symbolic representation of the species after fractionation, and the spectra of the various fractions/phases compared to define a comparative spectrum as a marker or otherwise providing information about the sample, including such information that is independent of the original level of abundance of the molecules in the mixture. Comparative spectra of various samples can be compared to each other and/or to controls or reference spectra and/or comparative spectra to determine a variety of information. In some embodiments, the methods can be used for discovering and/or identifying patterns in a mixture of species and/or corresponding patterns of species in a second mixture, where each mixture of species originates from biological systems with different physiological conditions as markers associated with specific diagnostics, and can be used for screening for such markers once discovered and identified during diagnostics screening.