Nano-electrospray ionization mass spectrometry: addressing analytical problems beyond routine

The advent of nano-electrospray ionization (nano-ESI) has considerably extended the usability of ESI in the analytical mass spectrometric laboratory. One of the remarkable features of nano-ESI is its extremely low sample consumption. Only a few microliters of analyte solution (10–5–10–8 M) are sufficient for molecular weight determination and structural investigations by MS/MS. But nano-ESI is more than just a minimized-flow ESI; the low solvent flow rate also affects the mechanism of ion formation. As a consequence, the area of ESI-MS applications is significantly enhanced. Oligosaccharides, glycosides as well as glycoproteins can be analyzed more easily than with normal ion spray. The same holds for the analysis of non-covalent complexes sprayed directly from aqueous solutions.