Czech J. Food Sci., 2004, 22(10):S144-S146 | DOI: 10.17221/10639-CJFS

Determination of stigmasterol hydroperoxides using high-performance liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization

S. Kemmo, V. Ollilainen, A.-M. Lampi, V. Piironen

Department of Applied Chemistry and Microbiology, Division of Food Chemistry, University of Helsinki, Finland

A new specific method using high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the detection of stigmasterol hydroperoxides was developed. Hydroperoxides of stigmasterol were obtained by photo-oxidation (90 min) in the presence of methylene blue as a sensitizer. The separation was performed using normal-phase chromatographic conditions. The MS detection was carried out with an ion-trap mass spectrometer using atmospheric pressure chemical ionization (APCI) and positive ion mode. Stigmasterol hydroperoxides were seen to produce no protonated molecular ions [M + H]⁺ but instead fragments representing loss of one or two water molecules [M - H₂O + H]⁺, [M - 2H₂O + H]⁺, loss of hydrogen peroxide [M - H₂O₂ + H]⁺ or loss of hydrogen peroxide and water [M - H₂O₂ - H₂O + H]⁺. The results showed that positional isomers of hydroperoxides had different fragmentation patterns and relative ion abundances. On the other hand anomeric isomers had more similar fragmentation. As a conclusion the method developed showed to be a useful tool for investigation the oxidation mechanism of sterols.

Keywords: HPLC-MS; APCI; stigmasterol; hydroperoxide

Published: December 31, 2004  Show citation