EVALUATION OF SOLID-PHASE EXTRACTION PROCEDURES IN PEPTIDE ANALYSIS

Solid-phase extraction (SPE) procedures for peptide isolation and frac tionation, based on non-polar and ionic interactions, were evaluated u sing small synthetic peptides and casein enzymatic hydrolysates. SPE b ased on hydrophobic phases is a useful, efficient and rapid procedure for peptide extraction and concentration. It allows a successful pepti de fractionation using eluents that contain an increasing content of a cetonitrile in the presence of trifluoroacetic acid. Differences regar ding selectivity are observed between sorbents. Non-polar interaction with C-18 sorbents is adequate for the isolation of very polar and hyd rophobic peptides. CN sorbents are only adequate for very hydrophobic peptides, PH, CH, C-8 and C-2 sorbents are useful for isolating and fr actionating hydrophobic and very non-polar peptides, but generally not for very polar peptides. Ionic solid-phase extraction using Accell Pl us cartridges of QMA (quaternary methylammonium) and CM (carboxymethyl ) are very useful for the fractionation of peptide mixtures into basic , acidic and neutral pools of peptides. It can be concluded that SPE u sing these procedures is a useful tool for the isolation and fractiona tion of peptides from biological and food samples.