Optimization of a pressurized liquid junction nanoelectrospray interface between CE and MS for reliable proteomic analysis

A pressurized liquid junction nano electrospray interface was designed and optimized for reliable on-line CE-MS coupling. The system was constructed as an integrated device for highly sensitive and selective analyses ofproteins and peptides with the separation and spray capillaries fixed ina pressurized spray liquid reservoir equipped with the electrode for connection of the electrospray potential. The electrode chamber on the injection side of the separation capillary and the spray liquid reservoir were pneumatically connected by a Teflon tube filled with pressurized nitrogen. This arrangement provided precisely counterbalanced pressures at the inlet and outlet of the separation capillary. The pressure control system was driven by an electrically operated valve and maintained the optimum flowrate for the electrospray stability. All parts of the interface being in contact with the CEBGE, spray liquid and/or sample were made of glass or Teflon. The use of these materials minimized the electrospray chemical noise often caused by plastic softeners or material degradation. During optimization, the transfer of the separated zones between the separation and electrospray capillaries was