18 Organic compounds in soils, sediments & sludges
Dreger et al [73] shows that the analysis of PAH in peat samples is complicated
by the high content of organic matter in peat which affects both extraction efficiency
and analytical quality. They evaluated the efficiencies of three extraction methods
(accelerated solvent extraction, fluidized bed extraction, ultrasound extraction) and
several clean-up techniques in order to find the best method. Accelerated solvent
extraction proved to be the best extraction method. For clean-up, a procedure using
aluminium oxide and silica gel showed the highest efficiency, whereas a method originally developed for soil samples failed to remove the peat matrix satisfactorily. With
overall recovery rates between 69 ± 14 and 89 ± 16% and an inaccuracy of <20%,
the optimised method was a suitable tool for the analysis of PAH in peat samples.
Subcritical water extraction
Hawthorne et al [61] coupled subcritical water extraction of polycyclic aromatic hydrocarbons with extraction using styrene-divinyl benzene extraction discs. The discs can
be stored in autosampler vials without loss of polycyclic aromatic hydrocarbons.
Accelerated solvent extraction
Saim et al [57] investigated the dependence of accelerated solvent extraction operating variable (pressure, temperature, extraction time) on the recovery of 16 polycyclic
aromatic hydrocarbons from native, contaminated soil. At the 95% confidence internal, no significance in terms of the three parameters was found regarding the total
polycyclic aromatic hydrocarbon recovery. However, when individual polycyclic aromatic hydrocarbons were considered, some compounds were found to be dependent
on operating variables. The most significant operating variable was extraction temperature. Low extraction temperature (40
◦ C) was found to be significant for naphthalene
chrysene, and benzo[b]fluorathene. Using consistent operating conditions (100
◦ C,
14 MPa and an extraction time of five minutes plus five minutes of equilibration time),
the influence of extraction solvent was evaluated. No dependence on recovery was
found when polar organic solvents, i.e., a dipole moment of ∼1.89, were used.
Accelerated solvent extraction is a new technique for the extraction of a range of
organic pollutants from soils, and related material. The technique is based on the use of
a solvent or combination of solvents to extract organic pollutants at elevated pressure
and temperature from a solid matrix. The range of organic pollutants for which the
technique is proposed includes semi volatile compounds, organochlorine pesticides,
organophosphorus pesticides, chlorinated herbicides, polychlorinated biphenyls and
polycyclic aromatic hydrocarbons [58–60].
Supercritical fluid extraction
Langenfeld et al [62] studied the effect of temperature and pressure on the supercritical
fluid extraction efficiencies of polyaromatic hydrocarbons and polychlorobiphenyls in
soils. At 50
◦ C raising the pressure from 350 to 650 atm had no effect on recoveries.
Burford et al [63] studied extraction rates of spiked versus native polyaromatic
hydrocarbons from heterogeneous environmental samples using supercritical fluid
extraction and sonication in methylene chloride. Relative extraction rates of native
Dreger et al [73] shows that the analysis of PAH in peat samples is complicated
by the high content of organic matter in peat which affects both extraction efficiency
and analytical quality. They evaluated the efficiencies of three extraction methods
(accelerated solvent extraction, fluidized bed extraction, ultrasound extraction) and
several clean-up techniques in order to find the best method. Accelerated solvent
extraction proved to be the best extraction method. For clean-up, a procedure using
aluminium oxide and silica gel showed the highest efficiency, whereas a method originally developed for soil samples failed to remove the peat matrix satisfactorily. With
overall recovery rates between 69 ± 14 and 89 ± 16% and an inaccuracy of <20%,
the optimised method was a suitable tool for the analysis of PAH in peat samples.
Subcritical water extraction
Hawthorne et al [61] coupled subcritical water extraction of polycyclic aromatic hydrocarbons with extraction using styrene-divinyl benzene extraction discs. The discs can
be stored in autosampler vials without loss of polycyclic aromatic hydrocarbons.
Accelerated solvent extraction
Saim et al [57] investigated the dependence of accelerated solvent extraction operating variable (pressure, temperature, extraction time) on the recovery of 16 polycyclic
aromatic hydrocarbons from native, contaminated soil. At the 95% confidence internal, no significance in terms of the three parameters was found regarding the total
polycyclic aromatic hydrocarbon recovery. However, when individual polycyclic aromatic hydrocarbons were considered, some compounds were found to be dependent
on operating variables. The most significant operating variable was extraction temperature. Low extraction temperature (40
◦ C) was found to be significant for naphthalene
chrysene, and benzo[b]fluorathene. Using consistent operating conditions (100
◦ C,
14 MPa and an extraction time of five minutes plus five minutes of equilibration time),
the influence of extraction solvent was evaluated. No dependence on recovery was
found when polar organic solvents, i.e., a dipole moment of ∼1.89, were used.
Accelerated solvent extraction is a new technique for the extraction of a range of
organic pollutants from soils, and related material. The technique is based on the use of
a solvent or combination of solvents to extract organic pollutants at elevated pressure
and temperature from a solid matrix. The range of organic pollutants for which the
technique is proposed includes semi volatile compounds, organochlorine pesticides,
organophosphorus pesticides, chlorinated herbicides, polychlorinated biphenyls and
polycyclic aromatic hydrocarbons [58–60].
Supercritical fluid extraction
Langenfeld et al [62] studied the effect of temperature and pressure on the supercritical
fluid extraction efficiencies of polyaromatic hydrocarbons and polychlorobiphenyls in
soils. At 50
◦ C raising the pressure from 350 to 650 atm had no effect on recoveries.
Burford et al [63] studied extraction rates of spiked versus native polyaromatic
hydrocarbons from heterogeneous environmental samples using supercritical fluid
extraction and sonication in methylene chloride. Relative extraction rates of native