Organic compounds in soils 21
all three petroleum hydrocarbon-contaminated soils. However, due to similarities
in fragmentation patters, tandem mass spectrometry of higher molecular weight
species (m/z ∼200) was unable to distinguish between the possibility of higher alkylsubstituted three-ringed polycyclic aromatic hydrocarbons and four-ringed polycyclic
aromatic hydrocarbons. The technique offers the direct, rapid determination and
characterisation of surface-bound polycyclic aromatic hydrocarbons in petroleumcontaminated soils at part per million levels without extraction, separation or other
sample preparation methods.
High-performance liquid chromatography HPLC
This technique, with fluorescence detection, has been applied by Reindl and Hoeffer
et al [64] and Lopez et al [79]. Liquid chromatography has also been employed [80–82].
HPLC with fluorescence detection gave results for polycyclic aromatic hydrocarbons which were comparable to those obtained by gas chromatography with mass
spectrometric detection.
This layer chromatography
Fowlie and Bulman et al [83] have carried out a detailed study of the extraction of
anthracene and benzo[a]pyrene from soil. They carried out a replicated factorial experiment using Soxhlet extraction and Polytron techniques. Soxhlet extraction followed
by thin layer chromatography gave higher recoveries of the two polyaromatic hydrocarbons. The soil samples were spiked with labelled and unlabelled benzo[a]pyrene or
anthracene at 5 and 50 µg/g soil. Subsamples were taken from each flask and extracted
by one of two methods: by overnight Soxhlet extraction with 1:1 hexane:acetone [84]
or by extraction in a Polytron homogeniser (Brinkman Instruments Ltd) with three
successive 24 mL portions of acetone [85].
Thin layer chromatography of the solvent extracts was carried out on silica
gel 250 µm plates. The plates were developed in ascending fashion with 1:1:1
hexane:acetone:toluene or hexane. of the labelled benzo[a]pyrene and anthracene.
Other techniques
Other techniques that have been used to determine polycyclic aromatic hydrocarbons
in soil extracts include ELISA field screening [86], micellar electrokinetic capillary
chromatography [87], supersonic jet laser-induced fluorescence [88, 89], fluorescence quenching [90], thermal desorption gas chromatography-mass spectrometry [90,
99], microwave-assisted extraction [91], thermal desorption [92], immunochemical
methods [93,94], electrophoresis [95], thin layer chromatography and pyrolysis gas
chromatography [32].
The addition of methanolic alkali or boron trifluoride methanol [96–98] as a modifier has been recommended for the extraction of polycyclic aromatic hydrocarbons
from soils containing a high proportion of humic acids.
Lichtfouse et al [97] and others [101, 102] demonstrated that polycyclic aromatic
hydrocarbons in soil are mainly pyrolytic in origin.
all three petroleum hydrocarbon-contaminated soils. However, due to similarities
in fragmentation patters, tandem mass spectrometry of higher molecular weight
species (m/z ∼200) was unable to distinguish between the possibility of higher alkylsubstituted three-ringed polycyclic aromatic hydrocarbons and four-ringed polycyclic
aromatic hydrocarbons. The technique offers the direct, rapid determination and
characterisation of surface-bound polycyclic aromatic hydrocarbons in petroleumcontaminated soils at part per million levels without extraction, separation or other
sample preparation methods.
High-performance liquid chromatography HPLC
This technique, with fluorescence detection, has been applied by Reindl and Hoeffer
et al [64] and Lopez et al [79]. Liquid chromatography has also been employed [80–82].
HPLC with fluorescence detection gave results for polycyclic aromatic hydrocarbons which were comparable to those obtained by gas chromatography with mass
spectrometric detection.
This layer chromatography
Fowlie and Bulman et al [83] have carried out a detailed study of the extraction of
anthracene and benzo[a]pyrene from soil. They carried out a replicated factorial experiment using Soxhlet extraction and Polytron techniques. Soxhlet extraction followed
by thin layer chromatography gave higher recoveries of the two polyaromatic hydrocarbons. The soil samples were spiked with labelled and unlabelled benzo[a]pyrene or
anthracene at 5 and 50 µg/g soil. Subsamples were taken from each flask and extracted
by one of two methods: by overnight Soxhlet extraction with 1:1 hexane:acetone [84]
or by extraction in a Polytron homogeniser (Brinkman Instruments Ltd) with three
successive 24 mL portions of acetone [85].
Thin layer chromatography of the solvent extracts was carried out on silica
gel 250 µm plates. The plates were developed in ascending fashion with 1:1:1
hexane:acetone:toluene or hexane. of the labelled benzo[a]pyrene and anthracene.
Other techniques
Other techniques that have been used to determine polycyclic aromatic hydrocarbons
in soil extracts include ELISA field screening [86], micellar electrokinetic capillary
chromatography [87], supersonic jet laser-induced fluorescence [88, 89], fluorescence quenching [90], thermal desorption gas chromatography-mass spectrometry [90,
99], microwave-assisted extraction [91], thermal desorption [92], immunochemical
methods [93,94], electrophoresis [95], thin layer chromatography and pyrolysis gas
chromatography [32].
The addition of methanolic alkali or boron trifluoride methanol [96–98] as a modifier has been recommended for the extraction of polycyclic aromatic hydrocarbons
from soils containing a high proportion of humic acids.
Lichtfouse et al [97] and others [101, 102] demonstrated that polycyclic aromatic
hydrocarbons in soil are mainly pyrolytic in origin.