124 Organic compounds in soils, sediments & sludges
paper and glass Soxhlet thimbles, and discuss the stability for multiple use of the two
materials for trace organic sample preparation.
Stobodnik et al [4] used a method based on sediment extraction using on-line solid
phased extraction followed by GCMS for the determination of organics in non-saline
sediments.
A further refinement is to reflux the sample with an acid or alkali and then solvent
extract the degradation products for identification. Thus treatment of fish with sulphuric acid followed by extraction with isopropanol-hexane enables chlorophenols,
chlorinated insecticides and polychlorostyrenes to be determined by gas chromatography. Fuming sulphuric acid treatment followed by hexane extraction facilitates the
determination of chlorinated insecticides.
Reflux with alcoholic potassium hydroxide followed by solvent extraction enables
hydrocarbons, polycyclicaromatic hydrocarbons and dioxins to be determined by gas
chromatographically in extracts of sediments.
Faure et al [5] have discussed the application of gel chromatography and ultra
filtration to the fractionation of organic substances in non-saline sediments. Extraction
of organic substances from sediments from the River Rhône, France, using caustic soda,
and by non-exchange resins, were compared, and their effect on fractionation by gel
chromatography determined. Ultra-filtration and gel chromatography of the extracts
were compared and the results are tabulated. The molecular distribution of organic
substances in Rhône water samples, concentrated by evaporation, was obtained by
using SEPHADEX gel for molecular weights below 700, and ultra-filtration for higher
molecular weights. Although the two fractionation methods give comparable results,
a combination of the two methods is recommended.
Other isolation techniques that have been used for organics include flash pyrolysisgas chromatography-mass spectrometry for the determination of polycyclicaromatic
hydrocarbons and polychlorinated biphenyls in sediments, headspace analysis-gas
chromatography-mass spectrometry for the determination of hydrocarbons and
volatile chloro compounds in sediments and miscellaneous organics in algae, and steam
distillation for the determination of non-volatile chlorocompounds in sediments and
supercritical fluid chromatography [6].
5.2 SALINE, MARINE SEDIMENTS
Sedimentary solid matter is of two main classes, that which is settled on the sea
bed or river bed and that which is present in suspension in the water column. The
former can be collected by hand in shallow waters or by using a suitable solid sampler in deeper waters as discussed by Butman [7]. Particulates present in samples
of the water column can be isolated by a variety of means including filtration and
centrifugation.
In the first place, it is generally agreed that the distribution of particle sizes in the
oceans is continuous, from the whale to the simple single molecule (Sharp [8, 9]. The
size at which one calls an aggregate of molecules a particle is therefore arbitrary. In the
case of sea water, the dividing line between dissolved and particulate has been chosen
as 0.45 µm largely because the first commercially available membrane filters had that
as their pore size.
paper and glass Soxhlet thimbles, and discuss the stability for multiple use of the two
materials for trace organic sample preparation.
Stobodnik et al [4] used a method based on sediment extraction using on-line solid
phased extraction followed by GCMS for the determination of organics in non-saline
sediments.
A further refinement is to reflux the sample with an acid or alkali and then solvent
extract the degradation products for identification. Thus treatment of fish with sulphuric acid followed by extraction with isopropanol-hexane enables chlorophenols,
chlorinated insecticides and polychlorostyrenes to be determined by gas chromatography. Fuming sulphuric acid treatment followed by hexane extraction facilitates the
determination of chlorinated insecticides.
Reflux with alcoholic potassium hydroxide followed by solvent extraction enables
hydrocarbons, polycyclicaromatic hydrocarbons and dioxins to be determined by gas
chromatographically in extracts of sediments.
Faure et al [5] have discussed the application of gel chromatography and ultra
filtration to the fractionation of organic substances in non-saline sediments. Extraction
of organic substances from sediments from the River Rhône, France, using caustic soda,
and by non-exchange resins, were compared, and their effect on fractionation by gel
chromatography determined. Ultra-filtration and gel chromatography of the extracts
were compared and the results are tabulated. The molecular distribution of organic
substances in Rhône water samples, concentrated by evaporation, was obtained by
using SEPHADEX gel for molecular weights below 700, and ultra-filtration for higher
molecular weights. Although the two fractionation methods give comparable results,
a combination of the two methods is recommended.
Other isolation techniques that have been used for organics include flash pyrolysisgas chromatography-mass spectrometry for the determination of polycyclicaromatic
hydrocarbons and polychlorinated biphenyls in sediments, headspace analysis-gas
chromatography-mass spectrometry for the determination of hydrocarbons and
volatile chloro compounds in sediments and miscellaneous organics in algae, and steam
distillation for the determination of non-volatile chlorocompounds in sediments and
supercritical fluid chromatography [6].
5.2 SALINE, MARINE SEDIMENTS
Sedimentary solid matter is of two main classes, that which is settled on the sea
bed or river bed and that which is present in suspension in the water column. The
former can be collected by hand in shallow waters or by using a suitable solid sampler in deeper waters as discussed by Butman [7]. Particulates present in samples
of the water column can be isolated by a variety of means including filtration and
centrifugation.
In the first place, it is generally agreed that the distribution of particle sizes in the
oceans is continuous, from the whale to the simple single molecule (Sharp [8, 9]. The
size at which one calls an aggregate of molecules a particle is therefore arbitrary. In the
case of sea water, the dividing line between dissolved and particulate has been chosen
as 0.45 µm largely because the first commercially available membrane filters had that
as their pore size.