Investigation of photochemical reactions of saccharides during direct ultraviolet absorbance detection in capillary electrophoresis.
Direct UV detection of saccharides in capillary electrophoresis is possible due to a base-catalyzed conversion into UV absorbing substances initiated by the light of the UV detector lamp. In the present study the compounds formed during this reaction were investigated with capillary electrophoresis using an additional UV lamp for online irradiation at a certain distance before the detector resulting in a separation of the conversion products. It was found that for all investigated saccharides (glucose, ribose and sucrose) the major portion of the UV absorption in direct UV detection resulted from one and the same substance. By CE-UV, CE-MS as well as HPLC-MS measurements this substance was demonstrated to be malondialdehyde, present as its conjugate base malonenolate under alkaline conditions. Additional experiments revealed that the conversion reaction is highly sensitive to the residence time under the UV light as malondialdehyde can further degrade into non-UV absorbing products. NMR measurements showed that under alkaline conditions this degradation proceeds slowly even without UV irradiation.
Johannes Kepler University Linz, Institute of Analytical Chemistry, Altenberger Straße 69, 4040 Linz, Austria. Electronic address: Thomas.Schmid@jku.at.
Thomas
T
Schmid
Johannes Kepler University Linz, Institute of Analytical Chemistry, Altenberger Straße 69, 4040 Linz, Austria.
Markus
M
Himmelsbach
University of Western Sydney, Australian Centre for Research on Separation Science (ACROSS), School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia; University of Western Sydney, Molecular Medicine Research Group, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
James D
JD
Oliver
University of Western Sydney, Australian Centre for Research on Separation Science (ACROSS), School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia; University of Western Sydney, Molecular Medicine Research Group, School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
Marianne
M
Gaborieau
University of Western Sydney, Australian Centre for Research on Separation Science (ACROSS), School of Science and Health, Locked Bag 1797, Penrith, NSW 2751, Australia.
Patrice
P
Castignolles
Johannes Kepler University Linz, Institute of Analytical Chemistry, Altenberger Straße 69, 4040 Linz, Austria.
Wolfgang
W
Buchberger
D002241:Carbohydrates / Q000032:analysis* / Q000737:chemistry* / Q000528:radiation effects; D019075:Electrophoresis, Capillary / Q000379:methods*; D008315:Malondialdehyde / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D010777:Photochemistry; D014466:Ultraviolet Rays
D002241:Carbohydrates; D008315:Malondialdehyde
Capillary electrophoresis; Direct UV detection; Malondialdehyde; Online irradiation; Reaction mechanism; Saccharide