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RADIOCARBON DATING OF ALKENONES FROM MARINE SEDIMENTS: I. ISOLATION PROTOCOL
Abstract
The chemical and isotopic compositions of long-chain (C36C39) 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 g C. The degree of alkenone unsaturation ( ) 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.
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 g C. The degree of alkenone unsaturation ( ) 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.