ISSN:
0951-4198
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
Liquid secondary-ion mass spectrometry (LSIMS) experiments were performed on a series of model quaternary ammonium chlorides [MQ+Cl-] in order to develop a strategy, via an understanding of cluster-ion formation, for recognition of quarternary ammonium structures. Model structures contained a single quaternary site and various other structural features (for example, conjugated quaternary systems and carboxylic acid groups), using amine hydrochlorides as controls. Cluster ions were examined with both positive- and negative-ion LSIMS, using a range of matrix modifiers. Precursor scans, or ‘molecular weight confirmation scans’, of MQ+ (the charged molecular ion of quaternary ammonium compounds) and [M+H]+ ions were used to assist in the observation of cluster ions and to unambiguously demonstrate precursor/product relationships. Positive-ion experiments typically showed dimeric clusters of [2MQ+ A]+ (A=anion) and [2MQ-H]+ ions, while negative ion experiments produced [MQ + 2A]- ions. Observation of these cluster ions coupled with the lack of an [M-H]- ion are a distinguishing feature of quaternary amines. Additional cluster ions were targeted for distinguishing between protonated amines and quaternary amonium compounds containing a carboxylic acid group. A strategy for recognizing and distinguishing quaternary ammonium structures using LSIMS is proposed, and some initial experiments with thermospray and electrospray are discussed.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/rcm.1290080113
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