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Improved Polycyclic Aromatic Hydrocarbon and n‑Alkane Determination in Speleothems through Cleanroom Sample Processing
journal contribution
posted on 2019-05-13, 00:00 authored by Elena Argiriadis, Rhawn F. Denniston, Carlo BarbanteInterest
in paleoenvironmental reconstructions from biomarkers
in speleothems is increasing, thanks in part to the capacity of speleothems
to grow continuously and to resist postdepositional alteration. In
particular, the possibility exists to link high-resolution and accurately
dated fire and vegetation records with isotopic data of climatic and
paleoenvironmental interactions at the local and regional scale. However,
the scarcity of existing methods for the quantification of organic
molecules in stalagmites, together with the issues of sample availability,
contamination, and low concentrations, complicate this approach. In
this work, we developed a novel method for the simultaneous determination
of 18 polycyclic aromatic hydrocarbons (PAHs) and 26 n-alkanes (C10–C35) and then tested it
on “clean” calcite and aragonite stalagmite samples
from cave KNI-51 in the Australian tropics. The method involves subsampling
by using a hand-held drill, complete dissolution of the matrix in
hydrochloric acid, then liquid–liquid extraction, and GC-MS
analysis. Sample preparation was carried out in a 10 000 class
clean room built entirely in stainless steel to avoid contamination.
Detection limits were 0.3–9 ng for PAHs and 6–44 ng
for n-alkanes. Measurable concentrations of fire-derived
PAH compounds, namely, phenanthrene, pyrene, benzo(e)pyrene, and indeno(123-cd)pyrene, were detected
in only one sample, which dates to the year ∼2004 CE, when
a fire burned vegetation over the cave; n-alkanes
were detected in all samples in the range C23–C35, with no odd–even preference.
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Keywords
hydrochloric acidcave KNI -51aragonite stalagmite samplesCleanroom Sample Processing Interest10 000 classpyrenespeleothemDetection limitsfire-derived PAH compoundsPolycyclic Aromatic Hydrocarbon26 n18 polycyclicalkanecontaminationvegetation recordsGC-MS analysisSample preparationAustralian tropicsMeasurable concentrationssample availabilitypaleoenvironmental interactionsCEpaleoenvironmental reconstructionspostdepositional alteration10 000novel method
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