Mass spectrometric analysis of nanoscale sample volumes extracted from open microchannels after sample preconcentration applied on amyloid beta peptides

A new instrumental concept for extraction of nanovolumes from open microchannels (dimensions 150 μm?×?50 μm, length 10 mm) manufactured on silicon microchips has been used in combination with a previously developed method for preconcentrating proteins and peptides in the open channels through electromigration. The extracted nanovolumes were further analyzed using nanoelectrospray ionization (nESI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) directly or with subsequent enzymatic protein digestion in a nanodroplet prior to the MS analysis. Preconcentration of the samples resulted in a 15-fold sensitivity increase in nESI for a neurotensin solution, and using MALDI-MS, amyloid beta (Aβ) peptides could be detected in concentrations down to 1 nM. The method was also successfully applied for detection of cell culture Aβ.