Ion trap mass spectrometry of trimethylsilylamides following gas chromatography

Abstract

Fatty acid amides are a class of compounds with newly discovered biological activity. The ion trap mass spectrometric characteristics of silylated fatty acid amides were examined. Silylation of primary fatty acid amides is required prior to gas chromatography owing to thermal instability of the underivatized compound. The trimethylsilylated amides do not yield a molecular ion under normal electron ionization conditions (70 eV). With methane as a chemical ionization gas, the [M + H]+ ion appears. The [M + H]+ ion also appears when the helium buffer gas pressure is increased in the ion trap. There are three fragments other than the [M + H]+ peak that are predominant in the ion trap mass spectra of these compounds. Two of the fragments have been reported previously, namely the m/ z 59 and the [M − 71]+ fragments. The fragment of m/ z 72 was identified and is the result of a rearrangement. Isotopic labeling was used to confirm fragment identity and the composition of the rearrangement products. Fragmentation patterns were affected by the amide chain length and concentration. Copyright © 2000 John Wiley & Sons, Ltd.

Mass Spectrometric Fragmentation of Trimethylsilyl and Related Alkylsilyl Derivatives

“…In contrast to the quadrupole spectrum, the spectrum recorded with an ion trap instrument (Fig. b), was very different (Gee et al, , ). Major ions were [M − 71] + and m/z 59 but the major ions, such as the McLafferty rearrangement ion at m/z 131 seen in the quadrupole spectrum, were absent.…”

Metabolism, Physiology, and Analyses of Primary Fatty Acid Amides

“…60 When using electron ionization, as found in gas chromatography instruments, the fragmentation pattern can be matched to standard databases for component identification. If PFAM fragmentation patterns are not provided in the database software, reports have been published of electron ionization fragmentation assignment of PFAM-TMS derivatives 61 or postcolumn mass spectra of collision-induced dissociation of PFAMs. 62 PFAM content in tallow was investigated by liquid chromatography atmospheric pressure chemical ionization mass spectrometry with a reported limit of detection of 18.5 fm.…”

Quantification of primary fatty acid amides in commercial tallow and tallow fatty acid methyl esters by HPLC-APCI-MS

“…The second most abundant mass peak detected at m/z 72 has been reported to derive from a homolytic cleavage in the aliphatic chain and a hydrogen transfer. 23…”

“…9 Mainly GC-MS investigations were performed on these compounds, to some extent using trimethylsilylation. 6,9,[22][23][24] These investigations used external standard calibration. Additionally, HPLC, 25,26 colorimetric 27 and spectrophotometric 28 methods are reported.…”