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Radiocarbon Dating of Alkenones from Marine Sediments: I. Isolation Protocol

Published online by Cambridge University Press:  18 July 2016

Naohiko Ohkouchi ,
Li Xu ,
Christopher M Reddy ,
Daniel Montluçon  and
Timothy I Eglinton
Naohiko Ohkouchi
Affiliation:
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
Li Xu
Affiliation:
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
Christopher M Reddy
Affiliation:
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
Daniel Montluçon
Affiliation:
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
Timothy I Eglinton*
Affiliation:
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
*
Corresponding author. Email: teglinton@whoi.edu.
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Abstract

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The chemical and isotopic compositions of long-chain (C36–C39) unsaturated ketones (alkenones), a unique class of algal lipids, encode surface ocean properties useful for paleoceanographic reconstruction. Recently, we have sought to extend the utility of alkenones as oceanic tracers through measurement of their radiocarbon contents. Here, we describe a method for isolation of alkenones from sediments as a compound class based on a sequence of wet chemical techniques. The steps involved, which include silica gel column chromatography, urea adduction, and silver nitrate-silica gel column chromatography, exploit various structural attributes of the alkenones. Amounts of purified alkenones estimated by GC/FID measurements were highly correlated with CO2 yields after sample combustion, indicating purities of greater than 90% for samples containing ≥ 100 μg C. The degree of alkenone unsaturation (U37K′) also varied minimally through the procedure. We also describe a high-performance liquid chromatography (HPLC) method to isolate individual alkenones for molecular-level structural and isotopic determination.

Type
Articles
Information
Radiocarbon , Volume 47 , Issue 3 , 2005 , pp. 401 - 412
Copyright
Copyright © 2005 by the Arizona Board of Regents on behalf of the University of Arizona 

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