42 Organic compounds in soils, sediments & sludges
and dibenzofurans and non-ortho polychlorobiphenyls are among the most toxic manmade or natural substances to a variety of animal species [240–243]. The toxic hazards
posed by these chemicals are exacerbated by their propensity to persist in the environment [255–257] and to readily bioaccumulate [258–260], and although the rate of
metabolism and elimination is strongly species-dependent [252], certain highly toxic
isomers have been observed to persist in the human body for more than ten years [261].
The majority of scientific and governmental concerns for the hazards of these
compounds have been directed towards analytical methodologies, toxicology, epidemiology and determination of the disposition in the environment for the single most toxic
isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin [240–245, 247].
Extraction methods
Von Bavel et al [152] have developed a solid-phase carbon trap (PX-21 active
carbon) for the simultaneous determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans as well as polychlorobiphenyls and chlorinated insecticides in
soils using superfluid extraction liquid chromatography for the final determination.
Walters and Guiseppe-Elie et al [262] studied the sorption of 2,3,7,8-tetra
chlorodibenzo-p-dioxin to soils from aqueous methanol mixtures and evaluated the
applicability of the cosolvent theory to such sorption. Sorption kinetics were influenced
by the fraction of methanol in the liquid phase and the soil type.
Onuska and Terry et al [263] used supercritical fluid chromatography to extract
dioxins from soil.
Richter et al [264] showed that accelerated solvent extraction gave essentially
equivalent recoveries of chlorinated dibenzo-p-dioxins and dibenzofurans from soil
compared to Soxhlet extraction, but in less time and using much less solvent.
No significant difference was found in the determination of chlorodibenzo-pdioxins and dibenzofurans in soil between Soxhlet extractions using toluene or
methylene chloride-acetone as extractants [265].
Hengstmann et al [266] studied five different extraction methods for the determination of chlorodioxins in soil and concluded that nearly quantitative extractions
could be achieved in two hours using “supersonic’’ Soxhlet.
Otaka et al [267, 268] have conducted detailed studies of the extractability from
soils of dioxins such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated dioxins biphenyls from humic acid in soil by
pressurised liquid extract, or with ether, toluene or acetone. The recovery rates of
dioxins by toluene from metal from the humic acid fraction varied with the organic
carbon content. Even with acetone the recovery of dioxins from metal-bound humic
acid was poor (11–40%). These results suggest that humic acid prevented the solvents
from accessing sequestered dioxins.
In further work Otaka et al [268] evaluated the effects of sample pre-treatment
on the extractability of polychlorinated dibenzo-p-dioxins (PCDDS), polychlorinated
dibenzofurans (PCDF’s) and coplanar polychlorinated biphenyls (CoPCBs) from three
suburban soil samples. The samples were treated with 0.1 M hydrochloric acid
or 0.1 M sodium hydroxide and extracted by pressurised liquid extraction with
toluene. In addition, untreated soil samples were subjected to pressurised liquid
extraction with acetone. The extractability values were compared to values obtained
and dibenzofurans and non-ortho polychlorobiphenyls are among the most toxic manmade or natural substances to a variety of animal species [240–243]. The toxic hazards
posed by these chemicals are exacerbated by their propensity to persist in the environment [255–257] and to readily bioaccumulate [258–260], and although the rate of
metabolism and elimination is strongly species-dependent [252], certain highly toxic
isomers have been observed to persist in the human body for more than ten years [261].
The majority of scientific and governmental concerns for the hazards of these
compounds have been directed towards analytical methodologies, toxicology, epidemiology and determination of the disposition in the environment for the single most toxic
isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin [240–245, 247].
Extraction methods
Von Bavel et al [152] have developed a solid-phase carbon trap (PX-21 active
carbon) for the simultaneous determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans as well as polychlorobiphenyls and chlorinated insecticides in
soils using superfluid extraction liquid chromatography for the final determination.
Walters and Guiseppe-Elie et al [262] studied the sorption of 2,3,7,8-tetra
chlorodibenzo-p-dioxin to soils from aqueous methanol mixtures and evaluated the
applicability of the cosolvent theory to such sorption. Sorption kinetics were influenced
by the fraction of methanol in the liquid phase and the soil type.
Onuska and Terry et al [263] used supercritical fluid chromatography to extract
dioxins from soil.
Richter et al [264] showed that accelerated solvent extraction gave essentially
equivalent recoveries of chlorinated dibenzo-p-dioxins and dibenzofurans from soil
compared to Soxhlet extraction, but in less time and using much less solvent.
No significant difference was found in the determination of chlorodibenzo-pdioxins and dibenzofurans in soil between Soxhlet extractions using toluene or
methylene chloride-acetone as extractants [265].
Hengstmann et al [266] studied five different extraction methods for the determination of chlorodioxins in soil and concluded that nearly quantitative extractions
could be achieved in two hours using “supersonic’’ Soxhlet.
Otaka et al [267, 268] have conducted detailed studies of the extractability from
soils of dioxins such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated dioxins biphenyls from humic acid in soil by
pressurised liquid extract, or with ether, toluene or acetone. The recovery rates of
dioxins by toluene from metal from the humic acid fraction varied with the organic
carbon content. Even with acetone the recovery of dioxins from metal-bound humic
acid was poor (11–40%). These results suggest that humic acid prevented the solvents
from accessing sequestered dioxins.
In further work Otaka et al [268] evaluated the effects of sample pre-treatment
on the extractability of polychlorinated dibenzo-p-dioxins (PCDDS), polychlorinated
dibenzofurans (PCDF’s) and coplanar polychlorinated biphenyls (CoPCBs) from three
suburban soil samples. The samples were treated with 0.1 M hydrochloric acid
or 0.1 M sodium hydroxide and extracted by pressurised liquid extraction with
toluene. In addition, untreated soil samples were subjected to pressurised liquid
extraction with acetone. The extractability values were compared to values obtained