Organic compounds in soils 19
polyaromatic hydrocarbons ranging from naphthalene M = 128 to benzo[b]fluoranthrene M = 252, and those of spiked deuterated polyaromatic hydrocarbons from
heterogeneous rail-road bed soil compared well with results obtained using sequential extraction with pure supercritical carbon dioxide or modified (10% methanol)
supercritical carbon dioxide and using sonication with methylene chloride.
Reindt and Hoffler et al [64] optimised parameters in the supercritical fluid extraction of polyaromatic hydrocarbons from soil. These workers used carbon dioxide
−8% methanol for extraction and obtained 88–101% recovery of polyaromatic
hydrocarbons in the final high-performance liquid chromatography.
Barnabas et al [65] have discussed an experimental design approach for the
extraction of polyaromatic hydrocarbons from soil using supercritical carbon dioxide.
They studied 16 different polyaromatic hydrocarbons using pure carbon dioxide and
methanol modified carbon dioxide. The technique is capable of determining down to
100 mg kg
−1 polyaromatic hydrocarbons in soils.
Tena et al [66] carried out a screening of polyaromatic hydrocarbon types of soil
by on-line fibre optic interfaced supercritical fluid extraction- spectrofluorimetry.
The apparatus incorporates a fibre optic interface for the spectrofluorimetric measurement on the supercritical carbon dioxide emerging from the extraction cell of a
supercritical fluid extractor, prior to depressurisation from up to 350 bar. Recoveries
of polyaromatic hydrocarbons are between 89 and 107% and measurements can be
carried on with a relative standard deviation of less than 5%.
Guo et al [71] have pointed out that whilst supercritical carbon dioxide is effective in extracting non-polar and slightly polar chemical such as polycyclic aromatic
hydrocarbons from soil it is unsatisfactory for recovering polar chemicals.
Gas chromatography
Extraction with benzene water followed by gas chromatography, pyrolysis gas
chromatography and gas chromatography [32] coupled with mass spectrometry
[75–78] have been applied to the determination of polycyclic aromatic hydrocarbons
in solvent extracts of soil.
Pyrloysis gas chromatography
The Curie Point flash evaporation-pyrloysis gas chromatography-mass spectrometric
[32] has been applied to the determination of the polyaromatic hydrocarbons. Analysis
of variance was used to assess the effects on polyaromatic hydrocarbons extraction at
the 99% confidence level. The percentage of
14 C in the extract and soil residue does
not total 100% because of degradation and volatilisation during incubation and due
to losses during analysis.
The data are presented in Table 2.1.
Significant differences at the 99% confidence level were observed for the extraction technique and for the polyaromatic hydrocarbons concentration in the soil.
The average recovery by the Soxhlet technique was 74.5%. A higher proportion was
extracted with polyaromatic hydrocarbons at the 50 µg/g level (72.6%) than at the
5 µg/g level (64.6%) suggesting that the extraction efficiency is not constant with
change in concentration.
polyaromatic hydrocarbons ranging from naphthalene M = 128 to benzo[b]fluoranthrene M = 252, and those of spiked deuterated polyaromatic hydrocarbons from
heterogeneous rail-road bed soil compared well with results obtained using sequential extraction with pure supercritical carbon dioxide or modified (10% methanol)
supercritical carbon dioxide and using sonication with methylene chloride.
Reindt and Hoffler et al [64] optimised parameters in the supercritical fluid extraction of polyaromatic hydrocarbons from soil. These workers used carbon dioxide
−8% methanol for extraction and obtained 88–101% recovery of polyaromatic
hydrocarbons in the final high-performance liquid chromatography.
Barnabas et al [65] have discussed an experimental design approach for the
extraction of polyaromatic hydrocarbons from soil using supercritical carbon dioxide.
They studied 16 different polyaromatic hydrocarbons using pure carbon dioxide and
methanol modified carbon dioxide. The technique is capable of determining down to
100 mg kg
−1 polyaromatic hydrocarbons in soils.
Tena et al [66] carried out a screening of polyaromatic hydrocarbon types of soil
by on-line fibre optic interfaced supercritical fluid extraction- spectrofluorimetry.
The apparatus incorporates a fibre optic interface for the spectrofluorimetric measurement on the supercritical carbon dioxide emerging from the extraction cell of a
supercritical fluid extractor, prior to depressurisation from up to 350 bar. Recoveries
of polyaromatic hydrocarbons are between 89 and 107% and measurements can be
carried on with a relative standard deviation of less than 5%.
Guo et al [71] have pointed out that whilst supercritical carbon dioxide is effective in extracting non-polar and slightly polar chemical such as polycyclic aromatic
hydrocarbons from soil it is unsatisfactory for recovering polar chemicals.
Gas chromatography
Extraction with benzene water followed by gas chromatography, pyrolysis gas
chromatography and gas chromatography [32] coupled with mass spectrometry
[75–78] have been applied to the determination of polycyclic aromatic hydrocarbons
in solvent extracts of soil.
Pyrloysis gas chromatography
The Curie Point flash evaporation-pyrloysis gas chromatography-mass spectrometric
[32] has been applied to the determination of the polyaromatic hydrocarbons. Analysis
of variance was used to assess the effects on polyaromatic hydrocarbons extraction at
the 99% confidence level. The percentage of
14 C in the extract and soil residue does
not total 100% because of degradation and volatilisation during incubation and due
to losses during analysis.
The data are presented in Table 2.1.
Significant differences at the 99% confidence level were observed for the extraction technique and for the polyaromatic hydrocarbons concentration in the soil.
The average recovery by the Soxhlet technique was 74.5%. A higher proportion was
extracted with polyaromatic hydrocarbons at the 50 µg/g level (72.6%) than at the
5 µg/g level (64.6%) suggesting that the extraction efficiency is not constant with
change in concentration.