Investigation of cationic organic dyes used as molecular probes by liquid secondary ion mass spectrometry

✍ Scribed by Richard E. Carlson; Kenneth L. Busch

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 737 KB
• Volume: 29
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210291110

✦ Synopsis

Abstract

The positive‐ion mass spectra of twelve organic dyes used as molecular probes were measured using liquid secondary ion mass spectrometry (LSIMS). Nine of the twelve dyes were singly charged cations and the other three were doubly charged cations. The mass spectra of each of the dyes in m‐nitrobenzyl alcohol contain abundant signals for the intact cation, C^+^ (singly charged cation dyes), or for singly‐charged forms of the doubly charged cation formed by proton loss, [C^2+^ H^+^]^+^, or halogen counter ion attachment, [C^2+^ + X^−^]^+^. Fragmentation is usually minimal under the conditions used. However, the cations of five of the singly charged compounds appear to undergo charge‐remote fragmentation. Collision‐induced dissociation experiments on a hybrid mass spectrometer of EBqQ geometry at collision energies up to 300 eV failed to access this fragmentation pathway. In contrast to the LSIMS of many other doubly charged organic compounds, two of the dicationic dyes produced a doubly charged ion of reasonable abundance (2–20%) in the mass spectrum. When glycerol was used as a matrix solvent, the addition of the matrix modifier trifluoroacetic acid increased the abundance of C^2+^.