Effects of molecular oxygen on multiphoton-excited photochemical analysis of hydroxyindoles.
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.
Gostkowski
M L
ML
Department of Chemistry and Biochemistry & The Institute for Cellular and Molecular Biology, University of Texas, Austin 78712, USA.
Curey
T E
TE
Okerberg
E
E
Kang
T J
TJ
Vanden Bout
D A
DA
Shear
J B
JB
D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry; D017785:Photons; D012701:Serotonin / Q000737:chemistry* / Q000378:metabolism
D012701:Serotonin; D010100:Oxygen