Sensitivity enhancement and second‐dimensional information from solid phase extraction‐capillary electrophoresis of entire high‐performance liquid chromatography fractions

A novel separation technique is demonstrated for peptide analysis of entire 100 μL high‐performance liquid chromatography (HPLC) fractions in a single, low pH, capillary zone electrophoresis (CZE) separation. The method employs a hybrid capillary consisting of a removable inlet section containing a reverse‐phase packing and a standard CZE bare‐fused silica separation capillary. The packed tip allows sample to be concentrated at flow rates greater than 20 μL/min and released in a controlled manner for CZE separation. Separations are comparable to standard CZE with minor modifications in selectivity. Using a mixture of model peptides, the hybrid capillary is shown to effect enhancement in sensitivity of ≥ 100‐fold. Five fractions from the HPLC separation of peptides obtained from the digestion of bovine serum albumin (BSA) were analyzed by the solid phase extraction‐capillary electrophoresis (SPE‐CE) method which was shown to provide rapid second‐dimensional information. Practical concentration limits of detection for peptides are calculated to be 1‐‐10 ng/mL with this technology.