Analysis of dilute peptide samples by capillary zone electrophoresis

We report a method for the analysis of dilute peptide solutions by capillary zone electrophoresis. The procedure is based on an electrophoretic concentration step of the applied peptide solution in the capillary (stacking) prior to separation, thus allowing the application of increased sample volumes without a breakdown in resolution. Given a constant configuration of the hardware, the method permits the analysis of peptide solutions of an at least 5 times lower concentration than previously possible. The method was applied to the direct analysis of peptide samples separated by narrow-bore reversed-phase high-performance liquid chromatography for high-sensitivity peptide-sequence analysis.