22 Organic compounds in soils, sediments & sludges
Rigon et al [103] used field-based supercritical fluid extraction an immunoassay
in a recent method for a determination of polycyclic aromatic hydrocarbon in soils.
The optimised extraction method was tested in field experiments on natural samples
with varying water content (0–32% w/w) without any sample pre-treatment, yielding an average PAH recovery of 80% against those obtained by Soxhlet extraction.
The immunoassay functioned in buffer-diluted 10% v/v methanol SFE extracts, allowing direct determination of polycyclic aromatic hydrocrbons with minimum sample
manipulation. Immunoassay served as a reliable semi-quantitative technique for rapid
screening of PAHs in supercritical fluid extraction preparations of natural soil samples
extracted in the field. Poor performance of the commercial solvent-shake extraction
(SSE) method further supported the on-site SFE/immunoassay method.
Polycyclic aromatic hydrocarbons in soil pore waters
Freely dissolved pore water concentrations are difficult to assess in complex matrixes
such as soils or sediments. Ter Leak et al [104] applied a negligible-depletion
partitioning – based sampling technique to measure freely dissolved pore water concentrations. A poly9dimethylsiloxane) (PDMS)-coated glass fibre was exposed to
a slurry of a soil spiked with several PAHs at concentration ranging from 2 to
2000 mg/kg. PAH-concentrations in the PDMS coating increased linearly with the
total soil concentration until a certain maximum was reached. Freely dissolved pore
water concentrations were calculated using PDMS-water partition coefficients, and the
calculated maximum pore water concentrations corresponded with the aqueous solubility of the tested compounds. Furthermore, the sampling technique is very sensitive
because it can detect freely dissolved pore water concentrations in the ng/L range for
the tested PAHs. Freely dissolved pore water concentrations are an important parameter for the exposure of organisms in soil. Saturation of the pore water with increasing
soil concentrations should therefore be considered in soil toxicity testing. Sorption
coefficients that were calculated from freely dissolved concentrations were slightly
higher than estimates based on octanol-water partition coefficients. These differences
are discussed in relation to the effects of dissolved matter in soil pore water on the
determination of sorption coefficients.
2.2 OXYGEN CONTAINING COMPOUNDS
2.2.1 Alcohols, ketones and aldehydes
Purge and trap gas chromatography
This technique has been applied [31] to the determination of ethanol, methylethyl
ketone, paraldehyde, and acrolein in soils. Following extraction of the soil with
methanol and gas purging the purge gas is trapped on a Tenax column. The purgate obtained by heating the Tenax column is analysed by gas chromatography and/or
mass spectrometry.
Langbehn et al [105] used supercritical fluid chromatography to determine organic
acids and ketones in soil.
Rigon et al [103] used field-based supercritical fluid extraction an immunoassay
in a recent method for a determination of polycyclic aromatic hydrocarbon in soils.
The optimised extraction method was tested in field experiments on natural samples
with varying water content (0–32% w/w) without any sample pre-treatment, yielding an average PAH recovery of 80% against those obtained by Soxhlet extraction.
The immunoassay functioned in buffer-diluted 10% v/v methanol SFE extracts, allowing direct determination of polycyclic aromatic hydrocrbons with minimum sample
manipulation. Immunoassay served as a reliable semi-quantitative technique for rapid
screening of PAHs in supercritical fluid extraction preparations of natural soil samples
extracted in the field. Poor performance of the commercial solvent-shake extraction
(SSE) method further supported the on-site SFE/immunoassay method.
Polycyclic aromatic hydrocarbons in soil pore waters
Freely dissolved pore water concentrations are difficult to assess in complex matrixes
such as soils or sediments. Ter Leak et al [104] applied a negligible-depletion
partitioning – based sampling technique to measure freely dissolved pore water concentrations. A poly9dimethylsiloxane) (PDMS)-coated glass fibre was exposed to
a slurry of a soil spiked with several PAHs at concentration ranging from 2 to
2000 mg/kg. PAH-concentrations in the PDMS coating increased linearly with the
total soil concentration until a certain maximum was reached. Freely dissolved pore
water concentrations were calculated using PDMS-water partition coefficients, and the
calculated maximum pore water concentrations corresponded with the aqueous solubility of the tested compounds. Furthermore, the sampling technique is very sensitive
because it can detect freely dissolved pore water concentrations in the ng/L range for
the tested PAHs. Freely dissolved pore water concentrations are an important parameter for the exposure of organisms in soil. Saturation of the pore water with increasing
soil concentrations should therefore be considered in soil toxicity testing. Sorption
coefficients that were calculated from freely dissolved concentrations were slightly
higher than estimates based on octanol-water partition coefficients. These differences
are discussed in relation to the effects of dissolved matter in soil pore water on the
determination of sorption coefficients.
2.2 OXYGEN CONTAINING COMPOUNDS
2.2.1 Alcohols, ketones and aldehydes
Purge and trap gas chromatography
This technique has been applied [31] to the determination of ethanol, methylethyl
ketone, paraldehyde, and acrolein in soils. Following extraction of the soil with
methanol and gas purging the purge gas is trapped on a Tenax column. The purgate obtained by heating the Tenax column is analysed by gas chromatography and/or
mass spectrometry.
Langbehn et al [105] used supercritical fluid chromatography to determine organic
acids and ketones in soil.