Letter: Hydroxide and oxygen atom attachment to dichlorophthalic anhydride in negative-ion chemical ionization with collisionally-activated dissociation in an external-source ion trap mass spectrometer

Eur. J. Mass Spectrom. 8, 329–332 (2002)
DOI: 10.1255/ejms.489

Hui-Fen Wu and Chien-Hung Chen
Department of Chemistry, Tamkang University, Tamsui, Taipei Hsien, 251, Taiwan

ABSTRACT:

This study reports the investigation of some unusual adduct ions of hydroxide and oxygen atoms in both negative-ion chemical ionization (NCI) and collisionally-activated dissociation (CAD) processes in an external-source ion trap mass spectrometer. The [M + OH]^– and [M + OH – Cl]^– adduct ions in the NCI spectrum of 4,5-dichlorophthalic anhydride are attributed to an ion/molecule reaction due to the presence of trace amounts of water. The formation of the unusual [M + O – Cl]^– ions during CAD of the M^– ions from 3,6- and 4,5-dichlorophthalic anhydride isomers is attributed to reactive collisions of the fragment ions with residual oxygen.

Keywords: negative chemical ionization (NCI), ion trap mass spectrometer (ITMS), collisionally activated dissociation (CAD)

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