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Identification and quantification of polyfunctionalized hopanoids by high temperature gas chromatography–mass spectrometry

Sessions, Alex L. and Zhang, Lichun and Welander, Paula V. and Doughty, David and Summons, Roger E. and Newman, Dianne K. (2013) Identification and quantification of polyfunctionalized hopanoids by high temperature gas chromatography–mass spectrometry. Organic Geochemistry, 56 . pp. 120-130. ISSN 0146-6380. PMCID PMC3780965. doi:10.1016/j.orggeochem.2012.12.009.

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Hopanoids are triterpenoids produced mainly by bacteria, are ubiquitous in the environment, and have many important applications as biological markers. A wide variety of related hopanoid structures exists, many of which are polyfunctionalized. These modifications render the hopanoids too involatile for conventional gas chromatography (GC) separation, so require either laborious oxidative cleavage of the functional groups or specialized high temperature (HT) columns. Here we describe the systematic evaluation and optimization of a HT–GC method for the analysis of polyfunctionalized hopanoids and their methylated homologs. Total lipid extracts are derivatized with acetic anhydride and no further treatment or workup is required. We show that acid or base hydrolysis to remove di- and triacylglycerides leads to degradation of several BHP structures. DB-XLB type columns can elute hopanoids up to bacteriohopanetetrol at 350 °C, with baseline separation of all 2-methyl/desmethyl homologs. DB-5HT type columns can additionally elute bacteriohopaneaminotriol and bacteriohopaneaminotetrol, but do not fully separate 2-methyl/desmethyl homologs. The method gave 2- to 7-fold higher recovery of hopanoids than oxidative cleavage and can provide accurate quantification of all analytes including 2-methyl hopanoids. By comparing data from mass spectra with those from a flame ionization detector, we show that the mass spectromet (MS) response factors for different hopanoids using either total ion counts or m/z 191 vary substantially. Similarly, 2-methyl ratios estimated from selected-ion data are lower than those from FID by 10–30% for most hopanoids, but higher by ca. 10% for bacteriohopanetetrol. Mass spectra for a broad suite of hopanoids, including 2-methyl homologs, from Rhodopseudomonas palustris are presented, together with the tentative assignment of several new hopanoid degradation products.

Item Type:Article
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URLURL TypeDescription CentralArticle
Sessions, Alex L.0000-0001-6120-2763
Summons, Roger E.0000-0002-7144-8537
Newman, Dianne K.0000-0003-1647-1918
Additional Information:© 2012 Elsevier Ltd. Received 30 May 2012. Received in revised form 6 December 2012. Accepted 17 December 2012. Available online 29 December 2012. Research at Caltech was supported by Grants from the NASA Exobiology program (NNX07AN49G and NNX12AD93G) to A.L.S. and D.K.N. Research at MIT was supported by Grants from the NSF Program on Emerging Trends in Biogeochemical Cycles (OCE-0849940), the NASA Astrobiology Institute, and a NASA Postdoctoral Program Fellowship to P.V.W. D.K.N. is an Investigator of the Howard Hughes Medical Institute. We thank M. Blumenberg and M. Elvert for constructive reviews of the manuscript.
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Howard Hughes Medical Institute (HHMI)UNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
PubMed Central ID:PMC3780965
Record Number:CaltechAUTHORS:20130503-154036933
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Official Citation:Alex L. Sessions, Lichun Zhang, Paula V. Welander, David Doughty, Roger E. Summons, Dianne K. Newman, Identification and quantification of polyfunctionalized hopanoids by high temperature gas chromatography–mass spectrometry, Organic Geochemistry, Volume 56, March 2013, Pages 120-130, ISSN 0146-6380, 10.1016/j.orggeochem.2012.12.009. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38274
Deposited By: Ruth Sustaita
Deposited On:03 May 2013 22:55
Last Modified:09 Nov 2021 23:36

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