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  • Collision-induced dissociation studies of caffeine in positive electrospray ionisation mass spectrometry using six deuterated isotopomers and one N1-ethylated homologue.

Collision-induced dissociation studies of caffeine in positive electrospray ionisation mass spectrometry using six deuterated isotopomers and one N1-ethylated homologue.

Rapid communications in mass spectrometry : RCM (2013-03-16)
Dirk Bier, Rudolf Hartmann, Marcus Holschbach
ABSTRACT

In order to deepen the understanding of electrospray ionisation collision-induced dissociation (ESI-CID) fragmentation reactions of xanthine derivatives for the identification of metabolites using low-resolution liquid chromatography/mass spectrometry (LC/MS) analysis, basic experiments using caffeine (1,3,7-trimethylxanthine) as model compound have been performed. Six deuterium isotopomers and one N1-ethylated homologue of caffeine have been synthesized and their ESI fragmentation spectra have been obtained by using LC/MS in combination with either standard or perdeuterated eluent mixtures. One result of these studies is the finding that the positive charges of the ESI-CID caffeine fragments are caused by the addition of protons. Furthermore, the performed experiments allow the determination of all molecular formulae of each ESI-CID caffeine fragment. As basic CID reactions of caffeine have been elucidated in this work, the developed fragmentation scheme may serve as a valuable tool for the interpretation of ESI-CID fragmentation spectra of more complex xanthine derivatives and their respective metabolites.

MATERIALS
Product Number
Brand
Product Description

Supelco
Caffeine solution, analytical standard, 1.0 mg/mL in methanol
Supelco
Melting point standard 235-237°C, analytical standard
Caffeine for system suitability, European Pharmacopoeia (EP) Reference Standard
Supelco
Caffeine solution, 1.0 mg/mL in methanol, ampule of 1 mL, certified reference material, Cerilliant®
Supelco
Caffeine, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Caffeine Melting Point Standard, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Caffeine, SAJ special grade, ≥98.5%
Supelco
Caffeine, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Sigma-Aldrich
Deuterium, 99.8 atom % D
Sigma-Aldrich
Caffeine, anhydrous, 99%, FCC, FG
Supelco
Mettler-Toledo Calibration substance ME 18872, Caffeine, traceable to primary standards (LGC)
Sigma-Aldrich
Deuterium, 99.96 atom % D
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Caffeine, powder, ReagentPlus®
Sigma-Aldrich
Caffeine, meets USP testing specifications, anhydrous
Sigma-Aldrich
Caffeine, Sigma Reference Standard, vial of 250 mg
Sigma-Aldrich
Caffeine, BioXtra
Sigma-Aldrich
Caffeine, anhydrous, tested according to Ph. Eur.
Sigma-Aldrich
Deuterium, 99.9 atom % D
Caffeine, European Pharmacopoeia (EP) Reference Standard