138 Organic compounds in soils, sediments & sludges
extractant, a composite substrate made of sand + soil + clay was spiked in a third
stage. Extractant composition was then evaluated in order to find out the minimum
volume of methyl alcohol that could be used without loss of efficiency. It was found
that 100% ethyl acetate matched these aims (% recovery >80) and the lowest use
of dichloromethane and methyl alcohol. Ultrasonic assisted extraction protocol was
tested in real sediments. The compounds were quantified by HPLC-FL and the identities were confirmed by gas chromatography-mass spectrometry. Identity of the HPLC
collected fractions for every single analyte was evaluated by means of GC-MS analysis. At least two injections from every sample extract measured by HPLC-FL were
performed (Figure 6.1).
No signs of interference came out during separation, which allowed an easy identification and quantification of the endocrine disrupting compounds (EDCs) under study
by comparing retention times and abundances of selected ions in standard solutions
and collected fractions. One target and three qualifier ions were selected to check out
the abundance pattern for each peak
Comparative chromatograms attained for different methods of extraction are
illustrated in Figure 6.2.
The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon
dating bulk organic carbon in lake sediments is often hampered by the old carbon effect,
i.e. the assimilation of ancient dissolvent inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed
on organic compounds derived from land plants that use atmosphere CO 2 which is
Rapidly delivered to sediments. Hou et al [97] demonstrated that lignin phenols isolated from lake sediments using reversed high performance liquid chromatography
(HPLC) can serve as effective
14 C dating materials for establishing chronology during
the late Quaternary. Hou et al [97] developed a procedure to purify lignin phenols.
By isolating lignin from standard wood reference substances, Hou et al [97] show
that their method yields pure lignin phenols and consistent ages as the consensus ages
and that their procedure does not introduce radiocarbon contamination. They further
demonstrated that lignin phenol ages are compatible with varve counted and macrofossil sediment horizons in Steel Lake and Fayettevlille Green Lake. Applying this
method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol
ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC)
ages which are contaminated by old carbon effect. It was also shown that the age offset
between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary
horizons, suggesting a variable hard water effect at different times and that a uniform
age correction throughout the core is inappropriate.
6.2.2 Carboxylic acids
Gas chromatography
Procedures for determining fatty acids in sediments involved liquid-liquid extraction,
liquid-liquid adsorption chromatography followed by gas liquid chromatographic
analysis [101]. Liquid extractions have been performed with methanol-chloroform,
methylene chloride [102] and benzene-methanol [103, 104]. Typical liquid-solid adsorbents are silicic acid. Standard gas chromatographic separations for complex mixtures
extractant, a composite substrate made of sand + soil + clay was spiked in a third
stage. Extractant composition was then evaluated in order to find out the minimum
volume of methyl alcohol that could be used without loss of efficiency. It was found
that 100% ethyl acetate matched these aims (% recovery >80) and the lowest use
of dichloromethane and methyl alcohol. Ultrasonic assisted extraction protocol was
tested in real sediments. The compounds were quantified by HPLC-FL and the identities were confirmed by gas chromatography-mass spectrometry. Identity of the HPLC
collected fractions for every single analyte was evaluated by means of GC-MS analysis. At least two injections from every sample extract measured by HPLC-FL were
performed (Figure 6.1).
No signs of interference came out during separation, which allowed an easy identification and quantification of the endocrine disrupting compounds (EDCs) under study
by comparing retention times and abundances of selected ions in standard solutions
and collected fractions. One target and three qualifier ions were selected to check out
the abundance pattern for each peak
Comparative chromatograms attained for different methods of extraction are
illustrated in Figure 6.2.
The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon
dating bulk organic carbon in lake sediments is often hampered by the old carbon effect,
i.e. the assimilation of ancient dissolvent inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed
on organic compounds derived from land plants that use atmosphere CO 2 which is
Rapidly delivered to sediments. Hou et al [97] demonstrated that lignin phenols isolated from lake sediments using reversed high performance liquid chromatography
(HPLC) can serve as effective
14 C dating materials for establishing chronology during
the late Quaternary. Hou et al [97] developed a procedure to purify lignin phenols.
By isolating lignin from standard wood reference substances, Hou et al [97] show
that their method yields pure lignin phenols and consistent ages as the consensus ages
and that their procedure does not introduce radiocarbon contamination. They further
demonstrated that lignin phenol ages are compatible with varve counted and macrofossil sediment horizons in Steel Lake and Fayettevlille Green Lake. Applying this
method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol
ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC)
ages which are contaminated by old carbon effect. It was also shown that the age offset
between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary
horizons, suggesting a variable hard water effect at different times and that a uniform
age correction throughout the core is inappropriate.
6.2.2 Carboxylic acids
Gas chromatography
Procedures for determining fatty acids in sediments involved liquid-liquid extraction,
liquid-liquid adsorption chromatography followed by gas liquid chromatographic
analysis [101]. Liquid extractions have been performed with methanol-chloroform,
methylene chloride [102] and benzene-methanol [103, 104]. Typical liquid-solid adsorbents are silicic acid. Standard gas chromatographic separations for complex mixtures