Organics
53
Lee et al. [93] used UV spectroscopy to identity PAHs in river sediments. The
procedure involved the collection of sediments, air drying in the dark, sieving, and
extraction for organic content. This was followed by column chromatography (silica
gel with cyclohexane as eluent), followed by a second chromatographic step with
Sephadex LH-20 and propan-2-01 as eluent. The eluate was then concentrated under
vacuum and prepared for ultraviolet analysis.
Marcomini et al. [94] applied gradient elution reversed-phase high performance
liquid chromatography coupled with a variable wavelength adsorption detector to 23
selected polycyclic hydrocarbons (including most of those on the EPA priority pollutant list) in radiodated sediment core. Compounds which were not separated by
chromatography were adequately resolved and quantified by performing three runs
per analysis using characteristic UV -visible absorption maxima. Detection limits
ranged from 0.1 to 1 Ilg kg- 1 dry weight, and the average recovery in spiking experiments was approximately 87 %, with the lowest yield for naphthalene (56 %).
Robbat et al. [731] carried out on-site detection of polycyclic aromatic hydrocarbons in hexane extract of sediments using thermal desorption gas chromatographymass spectrometry.
Lagenfeld et al. [755] studied the effect of temperature and pressure on supercritical
fluid extraction efficiencies of polyaromatic hydrocarbons and polychlorobiphenyls
in river sediments. At 50°C, raising the pressure from 350 to 650 atmospheres was
without effect on recovery from sediments.
Lagenfeld et al. [755] also compared supercritical monochlorodifluoromethane,
Nitrogen dioxide and carbon dioxide for the extraction of polyaromatic hydrocarbons
from sediments. Monochlorodifluoromethane provided the highest recoveries.
Hawthorne et al. [732] compared supercritical chlorodifluoromethane, nitrous
oxide and carbon dioxide for the extraction of polychlorobiphenyls from sediments.
Chlorodifluoromethane provided the highest recoveries, whilst methanol modified
carbon dioxide gave 90 % recovery of polychlorobiphenyls from sediments.
2.4.3
Phenols
Goldberg and Weiner [155] have described methods for the extraction and concentration of phenolic compounds from sediment. Lopez Avila et al. [130] have described a
microwave assisted extraction procedure for the separation of phenols from sediments.
2.4.4
Fatty Acids
Farrington and Quinn [95] gave details of procedures involving saponification and
extraction. Between 32 and 65 % of the fatty acids was not released from sediinents by
organic solvent extraction.
Other procedures for determining fatty acids in sediments involve liquid-liquid
extraction, liquid-solid adsorption chromatography followed by gas-liquid chromatographic analysis [96-98]. Liquid extractions have been performed with methanolchloroform [99], methylene chloride [100], and benzene-methanol [101-102]. Typical
53
Lee et al. [93] used UV spectroscopy to identity PAHs in river sediments. The
procedure involved the collection of sediments, air drying in the dark, sieving, and
extraction for organic content. This was followed by column chromatography (silica
gel with cyclohexane as eluent), followed by a second chromatographic step with
Sephadex LH-20 and propan-2-01 as eluent. The eluate was then concentrated under
vacuum and prepared for ultraviolet analysis.
Marcomini et al. [94] applied gradient elution reversed-phase high performance
liquid chromatography coupled with a variable wavelength adsorption detector to 23
selected polycyclic hydrocarbons (including most of those on the EPA priority pollutant list) in radiodated sediment core. Compounds which were not separated by
chromatography were adequately resolved and quantified by performing three runs
per analysis using characteristic UV -visible absorption maxima. Detection limits
ranged from 0.1 to 1 Ilg kg- 1 dry weight, and the average recovery in spiking experiments was approximately 87 %, with the lowest yield for naphthalene (56 %).
Robbat et al. [731] carried out on-site detection of polycyclic aromatic hydrocarbons in hexane extract of sediments using thermal desorption gas chromatographymass spectrometry.
Lagenfeld et al. [755] studied the effect of temperature and pressure on supercritical
fluid extraction efficiencies of polyaromatic hydrocarbons and polychlorobiphenyls
in river sediments. At 50°C, raising the pressure from 350 to 650 atmospheres was
without effect on recovery from sediments.
Lagenfeld et al. [755] also compared supercritical monochlorodifluoromethane,
Nitrogen dioxide and carbon dioxide for the extraction of polyaromatic hydrocarbons
from sediments. Monochlorodifluoromethane provided the highest recoveries.
Hawthorne et al. [732] compared supercritical chlorodifluoromethane, nitrous
oxide and carbon dioxide for the extraction of polychlorobiphenyls from sediments.
Chlorodifluoromethane provided the highest recoveries, whilst methanol modified
carbon dioxide gave 90 % recovery of polychlorobiphenyls from sediments.
2.4.3
Phenols
Goldberg and Weiner [155] have described methods for the extraction and concentration of phenolic compounds from sediment. Lopez Avila et al. [130] have described a
microwave assisted extraction procedure for the separation of phenols from sediments.
2.4.4
Fatty Acids
Farrington and Quinn [95] gave details of procedures involving saponification and
extraction. Between 32 and 65 % of the fatty acids was not released from sediinents by
organic solvent extraction.
Other procedures for determining fatty acids in sediments involve liquid-liquid
extraction, liquid-solid adsorption chromatography followed by gas-liquid chromatographic analysis [96-98]. Liquid extractions have been performed with methanolchloroform [99], methylene chloride [100], and benzene-methanol [101-102]. Typical