Two‐dimensional microfabricated sources for nanoelectrospray

The idea of a novel two‐dimensional (2D) nanoelectrospray ionization emitter tip with the shape of a nib is explored here. This novel planar design is studied as an alternative to the needle‐like standard emitter tips that suffer from a lack of reproducibility and robustness and from an inherent incompatibility with high‐throughput analysis. The composition of the micro‐nib sources is analogous to the working of a simple fountain pen, with a liquid reservoir linked to a micro‐nib tip from which the sample is electrosprayed via a capillary slot. The micro‐nib prototypes described here were fabricated using microtechnology techniques and using the epoxy‐based negative photoresist SU‐8. The resulting free‐standing micro‐nib structure was supported by a silicon wafer. We present here two series of such micro‐nib sources, the latter series exhibiting improved characteristics such as a 8 µm source width of the nib tip. They were tested in mass spectrometry experiments on an ion trap mass spectrometer (LCQ Deca XP+, Thermo Finnigan) using standard peptide samples having concentrations down to 1 µM and with a high voltage (HV) supply around 1 kV for the second series of micro‐nib sources. In addition to the stability of the spray, the obtained mass spectra showed the reliability of these sources for peptide analysis; the signal of the spectra was as intense and the signal‐to‐noise ratio (S/N) as high as that obtained with the use of standard emitter tips. Copyright © 2003 John Wiley & Sons, Ltd.