Liquid chromatography/mass spectrometry of peptides of biological samples

This review is focused on the Chromatographic methods of liquid chromatography-mass spectrometry (LC-MS) applied in the analysis of peptides in biological/biochemical samples. In particular, publications of the 1990s are selected that make use of electrospray ionization (ESI). The revolutionary development of the MS technique brought about by the new ESI sources and MS systems now makes it possible not only to register the molecular masses of peptides in a single LC run, but also to gain information on their amino acid sequences on-line. The features of ESI/MS systems (MS detector) and its requirements on the LC procedures are described. Sample clean-up procedures useful in peptide LC-MS both on-line and off-line are reviewed since peptide samples from biosystems should be enriched and also contaminants (salts, detergents) not compatible with the MS systems should be removed. Further, we report here on the optimum LC set-ups for on-line coupling to the MS systems, on the columns and the mobile phases suitable for peptide LC-MS. Included are the micro systems for low flow LC-ESI/MS that operate in the nl to pl min−1 flow range and are able to analyze attomolar amounts and lower nanomolar to picomolar concentrations of peptides.