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Electron impact, chemical ionization and collisional activation mass spectrometry of methyl O ‐acetyl‐β‐ D ‐xylopyranosides
Author(s) -
Kováčik Vladimír,
Petráková Eva,
Mihálov Vincent,
Tvaroška Igor,
Heerma Wigger
Publication year - 1985
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200120202
Subject(s) - mass spectrometry , electron ionization , ionization , chemical ionization , chemistry , analytical chemistry (journal) , atomic physics , physics , ion , chromatography , organic chemistry
The mass spectrometric behaviour of methyl O ‐acetyl‐β‐ D ‐xylopyranosides has been studied using electron impact, methane and ammonia chemical ionization and collisional activation mass spectrometry. Based on this study the fragmentation of the compounds studied has been described. The structures of ions occurring after elimination of ketene in the fragmentation reactions of acetylated saccharides were studied by using the MNDO semi‐empirical quantum chemical method. Calculated geometrical parameters (bond lengths, bond and torsional angles), distribution of net atomic charges and the difference in heat of formation (70 kJ mol −1 ) between the keto and enol isomers of [C 5 H 7 O 3 ] + ions studied predict that the enol structure is more stable thermodynamically than its corresponding keto isomer. The electron impact and chemical ionization mass spectra do not provide complete information for determination of the location of acetyl groups in methyl O ‐acetylpentopyranosides. The number and position of the acetyl groups however, can be determined unambiguously from collisional activation mass spectra of the [M ‐ OCH 3 ] + ions. The reproducibility of the mass spectral data, obtained by the applied mass spectral methods was evaluated by calculation of discrepancy factors. From this point of view the collisional activation method is approximately five times more precise than electron impact and 10 times more precise than chemical ionization methods.