25th International Meeting on Organic Geochemistry IMOG 2011

P-018
Evaluation of accelerated solvent extraction (ASE) for pigment
extraction from lake and marine sediments
Neungrutai Saesaengseerung, Brendan Keely
University of York, York, United Kingdom (corresponding author:ns540@york.ac.uk)
Chlorophylls and their derivatives are widely
occurring biomarkers for the primary producer
communities in lake and marine sediments. Their
abundances and distributions have been related to
the intensity of palae-production at the time of the
deposition 1 and to changes in relative sea level 2 and
ice cover 3 . Generally, analysis of these compounds in
sediments involves solvent extraction followed by
identification using liquid chromatography coupled
with photodiode array detection and mass
spectrometry.
Sonic extraction is the conventional method for
recovery of these sensitive pigments from lake and
marine sediments 2,3,4 . Although the method gives high
yields of extract, it is time consuming and is not
readily amenable to automation, a limitation to the use
of pigments in profiling at high sampling rates.
Accelerated solvent extraction (ASE) enhances
extraction efficiency by using elevated temperature
and pressure with liquid solvents to reduce extraction
times and solvent consumption 5 . It is becoming widely
utilisted in geochemistry for extraction from ancient
sediments because of the potential for automation.
Although the method offers potential advantages, its
suitability for extraction of the highly sensitive chlorin
pigments has not been tested.
To evaluate the applicability of ASE for chlorin
extraction from lake and marine environments,
sediments from several distinct locations were
extracted by sonic extraction and ASE over series of
temperatures (RT to 175�C). Pigments extracts were
analysed by LC/MS n and components identified on the
basis of their HPLC retention times and their online
UV/Vis and multistage tandem mass spectra. Total
yields of pigments and the formation of structural
alteration products are considered to evaluate the
potential use of ASE in pigment analysis.
Pigment quantification indicates that the total
yields of pigments from ASE and from sonic
extraction do not different significantly for ASE
temperatures around 80�C. At high temperatures
alteration of the pigment structure occurs during ASE
extraction; for example, demetallation of chlorophyll a,
forming phaeophytin a, and decarbomethoxylation at
C13 2 -phaeophytin a forming to pyrophaeophytin a
(Figure 1)
O
N N
N
Mg
N
O O
OMe
OPhytyl
demetallation
- Mg
O
NH N
N
HN
O O
OMe
OPhytyl
decarbomethoxylation
-COOMe
O
NH N
N
HN
OPhytyl
Chlorophyll a Phaeophytin a Pyrophaeophytin a
Figure1: Alteration of pigments in Lake Reid sediment
extraction by the ASE 150�C.
In addition to chlorophylls and their derivatives,
representing oxygenic primary producers, bacterio-
chlorophylls and their derivatives, representing
anoxygenic photoautrophs, have been examined in
the ASE suitability study for sediment extraction.
At the optimised ASE conditions, extraction time
and solvent consumption are reduced, leading to
increases in efficiency. Furthermore, the high
throughput and ability to automate the extraction
enables the profiling of sediment cores at higher
sampling resolutions within reasonable timescales.
References
1. Harris, P.G., et al., (1996), Nature, 383(6595), 63.
2. Squier, A.H., et al., (2002), Organic Geochemistry,
33(12), 1655.
3. Squier, A.H., et al., (2004), Organic Geochemistry,
35(2), 203.
4. Airs, R.L., et al., (2001), Journal of Chromatography A,
917(1-2), 167.
5. Richter, B.E., et al., (1996), Analytical Chemistry,
68(6), 1033.
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