Chemistry and Physics Faculty Articles

Title

Multistage Reactive Transmission-Mode Desorption Electrospray Ionization Mass Spectrometry

Document Type

Article

Publication Date

9-2015

Publication Title

Journal of the American Society for Mass Spectrometry

Keywords

Ambient mass spectrometry, Transmission-mode desorption electrospray ionization, Reaction monitoring, Mechanisms, Time scale, Catalysis, Iron porphyrin

ISSN

1044-0305

Volume

26

Issue/No.

9

First Page

1494

Last Page

1501

Abstract

Elucidating reaction mechanisms is important for advancing many areas of science such as catalyst development. It is often difficult to probe fast reactions at ambient conditions with high temporal resolution. In addition, systems involving reagents that cross-react require analytical methods that can minimize interaction time and specify their order of introduction into the reacting system. Here, we explore the utility of transmission mode desorption electrospray ionization (TM-DESI) for reaction monitoring by directing a microdroplet spray towards a series of meshes with micrometer-sized openings coated with reagents, an approach we call multistage reactive TM-DESI (TM n -DESI, where n refers to the number of meshes; n = 2 in this report). Various stages of the reaction are initiated at each mesh surface, generating intermediates and products in microdroplet reaction vessels traveling towards the mass spectrometer. Using this method, we investigated the reactivity of iron porphyrin catalytic hydroxylation of propranolol and other substrates. Our experimental results indicate that TM n-DESI provides the ability to spatially separate reagents and control their order of introduction into the reacting system, thereby minimizing unwanted reactions that lead to catalyst deactivation and degradation products. In addition, comparison with DESI-MS analyses (the Zare and Latour laboratories published results suggesting accessible reaction times <1 ms) of the reduction of dichlorophenolindophenol by L-ascorbic acid suggest that TM 1 -DESI can access reaction times less than 1 ms. Multiple meshes allow sequential stages of desorption/ionization per MS scan, increasing the number of analytes and reactions that can be characterized in a single experiment.

Comments

©American Society for Mass Spectrometry, 2015

Additional Comments

National Institutes of Health Chemistry-Biology Interface Training Program grant #: NIH T32 GM070421

DOI

10.1007/s13361-015-1171-5

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Peer Reviewed

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