| Issue |
J. Phys. Colloques
Volume 49, Number C6, Novembre 1988
35th International Field Emission Symposium / 35éme Symposium International d'Emission de Champ
|
|
|---|---|---|
| Page(s) | C6-233 - C6-236 | |
| DOI | https://doi.org/10.1051/jphyscol:1988639 | |
J. Phys. Colloques 49 (1988) C6-233-C6-236
DOI: 10.1051/jphyscol:1988639
COMPARISON OF BARE WIRES AND ACTIVATED EMITTERS FOR FD MS OF OLIGOSACCHARIDES
E. BRAMER-WEGER, N. TESCH et F.W. RÖLLGENInstitute of Physical Chemistry, University of Bonn, Wegelerstrasse 12, D-5300 Bonn 1, F.R.G.
Abstract
Ion formation in field desorption (FD) from activated wire emitters covered with field enhancing microneedles has been compared with that from bare wires for some oligosaccharides doped with NaCl. The experiment revealed a close similarity between both types of emitters in the ion formation by electrohydrodynamic disintegration processes at temperatures near the onset of ion emission. In contrast, at higher temperatures above the melting point the sample layers are removed from smooth wires while on activated emitters they are retained in part between the microneedles. In this temperature range surface mobile molecules were found to be ionized not only by FI processes on microneedle tips but also by alkali ion attachment on charged alkali ion donating solid deposits. The latter mechanism has not been considered in FD mass spectrometry yet.