28 Organic compounds in soils, sediments & sludges
An extraction temperature of 125
◦ C and ten-minute extractions performed three times
proved optimal. Two accelerated solvent extraction-solid-phase microextraction procedures without and with an organic modifier (5% acetonitrile) were evaluated with
respect to precision and detection limits.
Supercritical fluid extraction [129, 130] accelerated solvent extraction and subcritical fluid extraction [131] have been studied. To reduce the equipment cost and
the analysis time in the extraction process and sample preconcentration, a solid-phase
microextraction method was proposed by various workers [132–134]. Santos et al
[135] reduced both the use of organic solvents and the time-consuming clean-up and
preconcentration steps. They applied supercritical fluid extraction with carbon dioxide
as the extraction medium for sample preparation.
Purge and trap gas chromatography
Kester et al [31] discussed the application of the purge and trap gas chromatographic
method to the determination of chloroaromatic compounds such as chlorobenzenes,
1,2-dichlorobezene, 1,3-dichlorobenzene, bromobenzene in soils. Following methanol
extraction of the soil the extract was gas purged and the purge gases trapped on a
Tenax 1 silica gel-charcoal trap followed by thermal desorption from the trap and
examination by gas chromatography and/or mass spectrometry. The reproducibility
of replicate water extractions/sold-phase microextraction determination (n − 6) was in
the range of 7–20% relative standard deviation for the nine chlorophenols investigated.
Limit of detection values in the low ppb range were achieved for all chlorophenols.
Fourier transform infrared spectrometry
Yang and Her et al [136] used the principle of solid-phase microextraction combined
with Fourier transform infrared sensing to determine chlorinated organic compounds
in soil.
The sensing devise of this method was based on an infrared hollow waveguide,
the inner surface of which was coated with a hydrophobic film, Vaporised chlorinated
aromatic compounds from soils were trapped onto the hydrophobic film of the hollow
waveguide sampler following detection by Fourier transform infrared spectrometry.
The extraction process in this method was, in principle, similar to the headspace solidphase microextraction. Means of increasing the speed of transfer of the vaporised
organic species to the sampler were also studied. Results indicated that, with a negative
pressure on the end of the sample, the speed of transfer increased significantly. Vapour
pressures of the analytes were used as an indication in order to test the limitations
of this method in the analysis or organic compounds in soils. Results showed that
analytes with vapour pressures lower than 1600 Pa could be deducted quantitatively.
Typical R
2 values for the regression on the concentration and infrared signals were
around 0.99, and typical detection limits were in the range of hundreds of parts per
billion.
2.3.3 Chlorophenols
Chlorinated phenols are among the most important contaminants in the environment
(aqueous systems and soils) due to their widespread use in industry and agriculture
An extraction temperature of 125
◦ C and ten-minute extractions performed three times
proved optimal. Two accelerated solvent extraction-solid-phase microextraction procedures without and with an organic modifier (5% acetonitrile) were evaluated with
respect to precision and detection limits.
Supercritical fluid extraction [129, 130] accelerated solvent extraction and subcritical fluid extraction [131] have been studied. To reduce the equipment cost and
the analysis time in the extraction process and sample preconcentration, a solid-phase
microextraction method was proposed by various workers [132–134]. Santos et al
[135] reduced both the use of organic solvents and the time-consuming clean-up and
preconcentration steps. They applied supercritical fluid extraction with carbon dioxide
as the extraction medium for sample preparation.
Purge and trap gas chromatography
Kester et al [31] discussed the application of the purge and trap gas chromatographic
method to the determination of chloroaromatic compounds such as chlorobenzenes,
1,2-dichlorobezene, 1,3-dichlorobenzene, bromobenzene in soils. Following methanol
extraction of the soil the extract was gas purged and the purge gases trapped on a
Tenax 1 silica gel-charcoal trap followed by thermal desorption from the trap and
examination by gas chromatography and/or mass spectrometry. The reproducibility
of replicate water extractions/sold-phase microextraction determination (n − 6) was in
the range of 7–20% relative standard deviation for the nine chlorophenols investigated.
Limit of detection values in the low ppb range were achieved for all chlorophenols.
Fourier transform infrared spectrometry
Yang and Her et al [136] used the principle of solid-phase microextraction combined
with Fourier transform infrared sensing to determine chlorinated organic compounds
in soil.
The sensing devise of this method was based on an infrared hollow waveguide,
the inner surface of which was coated with a hydrophobic film, Vaporised chlorinated
aromatic compounds from soils were trapped onto the hydrophobic film of the hollow
waveguide sampler following detection by Fourier transform infrared spectrometry.
The extraction process in this method was, in principle, similar to the headspace solidphase microextraction. Means of increasing the speed of transfer of the vaporised
organic species to the sampler were also studied. Results indicated that, with a negative
pressure on the end of the sample, the speed of transfer increased significantly. Vapour
pressures of the analytes were used as an indication in order to test the limitations
of this method in the analysis or organic compounds in soils. Results showed that
analytes with vapour pressures lower than 1600 Pa could be deducted quantitatively.
Typical R
2 values for the regression on the concentration and infrared signals were
around 0.99, and typical detection limits were in the range of hundreds of parts per
billion.
2.3.3 Chlorophenols
Chlorinated phenols are among the most important contaminants in the environment
(aqueous systems and soils) due to their widespread use in industry and agriculture