Abstract: The present invention describes a method that combines the blocking of primary amino groups and the cation exchange chromatography, to simplify peptide mixtures that can be generated or not by proteolytic or chemical treatments. This method allows the selective isolation of an average of 4 multiply-charged peptides (RH peptides) per protein and the study of 90% of the proteins of the analyzed proteomes. It is applicable to studies of quantitative proteomics without the usage of two-dimensional electrophorsis, it is compatible with any type of isotopic labeling and it is very useful to determine the differential expression of proteins present in multiple conditions (3 to 6 conditions) when using different isotopic labeling in a single experiment. The chromatographic system used also allows the fractionation fraction of the RH peptides to achieve the identification of a greater number of proteins.