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Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry
Published on: June 14, 2018
Effects of molecular oxygen on multiphoton-excited photochemical analysis of hydroxyindoles
M L Gostkowski1, T E Curey, E Okerberg
1Department of Chemistry and Biochemistry & The Institute for Cellular and Molecular Biology, University of Texas, Austin 78712, USA.
Abstract:
We have examined the effects of dissolved molecular oxygen on multiphoton-excited (MPE) photochemical derivatization of serotonin (5HT) and related cellular metabolites in various buffer systems and find that oxygen has a profound effect on the formation efficiency of visible-emitting photoproducts. Previously, end-column MPE photoderivatization provided low mass detection limits for capillary electrophoretic analysis of hydroxyindoles, but relied on the use of Good's buffers to generate high-sensitivity visible signal. In the present studies, visible emission from 5HT photoderivatized in different buffers varied by 20-fold under ambient oxygen levels but less than 2-fold in the absence of oxygen; oxygen did not significantly alter the photoproduct excited-state lifetime (approximately 0.8 ns). These results support a model in which oxygen interferes with formation of visible-emitting photoproducts by quenching a reaction intermediate, an effect that can be suppressed by buffer molecules. Deoxygenation of capillary electrophoresis separation buffers improves mass detection limits for 5-hydroxyindoles fractionated in 600-nm channels by approximately 2-fold to < or =30000 molecules and provides new flexibility in identifying separation conditions for resolving 5HT from molecules with similar electrophoretic mobilities, such as the catecholamine neurotransmitters.
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