Publication Date:
2019-07-16
Description:
We describe the results of an inter-laboratory investigation
into the identification and quantification of the
Arctic sea ice biomarker proxy IP25 in marine sediments.
Seven laboratories took part in the study, which consisted of
the analysis of IP25 in a series of sediment samples from different
regions of the Arctic, sub-Arctic and Antarctic, additional
sediment extracts and purified standards. The results
obtained allowed 4 key outcomes to be determined. First,
IP25 was identified by all laboratories in sediments from the
Canadian Arctic with inter-laboratory variation in IP25 concentration
being substantially larger than within individual
laboratories. This greater variation between laboratories was
attributed to the difficulty in accurately determining instrumental
response factors for IP25, even though laboratories
were supplied with appropriate standards. Second, the identification
of IP25 by 3 laboratories in sediment from SW Iceland
that was believed to represent a blank, was interpreted
as representing a better limit of detection or quantification for
such laboratories, contamination or mis-identification. These
alternatives could not be distinguished conclusively with the
data available, although it is noted that the precision of these
data was significantly poorer compared with the other IP25
concentration measurements. Third, 3 laboratories reported
the occurrence of IP25 in a sediment sample from the Antarctic
Peninsula even though this biomarker is believed to be
absent from the Southern Ocean. This anomaly is attributed
to a combined chromatographic and mass spectrometric interference
that results from the presence of a di-unsaturated
highly branched isoprenoid (HBI) pseudo-homologue of IP25
that occurs in Antarctic sediments. Finally, data are presented
that suggest that extraction of IP25 is consistent between Accelerated
Solvent Extraction (ASE) and sonication methods
and that IP25 concentrations based on 7-hexylnonadecane as
an internal standard are comparable using these methods.
Recoveries of some more unsaturated HBIs and the internal
standard 9-octylheptadecene, however, were lower with
the ASE procedure, possibly due to partial degradation of
these more reactive chemicals as a result of higher temperatures
employed with this method. For future measurements,
we recommend the use of reference sediment material with
known concentration(s) of IP25 for determining and routinely
monitoring instrumental response factors. Given the significance
placed on the presence (or otherwise) of IP25 in marine
sediments, some further recommendations pertaining to
quality control are made that should also enable the two main
anomalies identified here to be addressed.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
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