Electron ionization mass spectrometry fragmentation and multiple reaction monitoring quantification of bacterial metabolites of the sea ice biomarker proxy IP 25 in Arctic sediments

• Published in: Rapid Communications in Mass Spectrometry
• Main Authors: Rontani, Jean‐François, Aubert, Claude, Belt, Simon T.
• Other Authors: Aix-Marseille Université, Centre National de la Recherche Scientifique
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Arctic; Sea ice
• Online Access: http://dx.doi.org/10.1002/rcm.8101; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Frcm.8101; http://onlinelibrary.wiley.com/wol1/doi/10.1002/rcm.8101/fullpdf

Rationale 3,9,13‐Trimethyl‐6‐(1,5‐dimethylhexyl)tetradecan‐1,2‐diol and 2,8,12‐trimethyl‐5‐(1,5‐dimethylhexyl)tridecanoic acid appear to be produced during the bacterial metabolism of IP 25 , a highly branched isoprenoid lipid often employed for past Arctic sea ice reconstruction. Characterization and quantification of these metabolites in sediments are essential to determine if bacterial degradation may exert a significant influence on IP 25 ‐based palaeo sea ice reconstructions. Methods Electron ionization mass spectrometry (EIMS) fragmentation pathways of 3,9,13‐trimethyl‐6‐(1,5‐dimethylhexyl)tetradecan‐1,2‐diol and 2,8,12‐trimethyl‐5‐(1,5‐dimethylhexyl)tridecanoic acid trimethylsilyl (TMS) derivatives were investigated. These pathways were deduced by: (i) low‐energy collision‐induced dissociation (CID) gas chromatography/tandem mass spectrometry (GC/MS/MS), (ii) accurate mass measurement, and (iii) deuterium labelling. Results CID‐MS/MS analyses, accurate mass measurement and deuterium‐labelling experiments enabled us to elucidate the EIMS fragmentations of 3,9,13‐trimethyl‐6‐(1,5‐dimethylhexyl)tetradecan‐1,2‐diol and 2,8,12‐trimethyl‐5‐(1,5‐dimethylhexyl)tridecanoic acid TMS derivatives. Some specific fragment ions useful in addition to chromatographic retention times for further characterization could be identified. As an application of some of the described fragmentations, the TMS derivatives of these metabolites were characterized and quantified in MRM mode in different Arctic sediments. Conclusions EIMS fragmentations of 3,9,13‐trimethyl‐6‐(1,5‐dimethylhexyl)tetradecan‐1,2‐diol and 2,8,12‐trimethyl‐5‐(1,5‐dimethylhexyl)tridecanoic acid TMS derivatives exhibit specific fragment ions, which appear to be very useful for the quantification of these bacterial metabolites of the palaeo tracer IP 25 in sediments.