Organic compounds in non-saline sediments 145
Chlorofluoromethane provided the highest recoveries while methanol modified carbon
dioxide gas 90% recovery of polychlorobiphenyls for sediments.
Herbert et al [122] used microwave-assisted extraction, combined with headspace
solid phase micro extraction and high resolution gas chromatography with ion-trap
tandem mass spectrometry to determine polychlorobiphenyls in sediments and soils.
Optimisation of the headspace solid phase micro extraction was carried out for the
most important parameters such as extraction time, sample volume and temperature.
The adopted methodology has reduced consumption of organic solvents and analysis
runtime. Under the optimised conditions, the method detection limit ranged from 0.6
to 1 ng/g when 5 g of sample was extracted, the precision on real samples ranged from
4 to 21% and the recovery from 69 to 104%. The proposed method, which included
the analysis of a certified reference material in its validation procedure, can be extended
to several other PCBs and used in the monitoring of soil or sediments for the presence
of PCBs.
Figure 6.3 shows the chromatographic separation of the selected PCBs in the
CP-Sil 8 analytical column obtained from a head space solid phase micro-extraction of
microwave assisted extracts from the CRM 536 (1 g extracted) and from a soil sample
(5 g extracted) collected in a landfill (42.8% humidity and 2.79% total organic matter
content).
The elution order obtained for PCBs compares to previously reported order for
PCBs within a homologue group on non-polar stationary phases according to the
number of ortho chlorines present.
Kominar et al [123] has described a method for the determination of polychlorobiphenyls in river sediments in which samples were extracted using ultrasonics into
1:1 n-hexane/acetone. The extract was partitioned with water and back extracted into
benzene. Combined organic extracts were dried on sodium sulphate, reduced in volume and cleaned up by gel permeation chromatography and silica gel partitioning.
Analysis of polychlorobiphenyls was carried out by gas chromatography with electron
capture detection.
Langenfeld et al [81, 133] studied the effect of temperature and pressure on
supercritical fluid efficiencies of polychlorinated biphenyls in river sediments. At a
temperature of 50
◦ C raising the pressure from 350 to 650 atmosphere had no beneficial effect on recovery of polychlorinated biphenyls from sediments. Recovery was
improved, however, as the extraction temperature was increased from 50
◦ C to 200
◦ C.
Langenfield et al [133] compared supercritical monochlorodifluoromethane,
nitrogen dioxide and carbon dioxide for the extraction of polychlorobiphenyls from
sediments. Monochlorodifluoromethane provided the highest recovery. Methanol
modified carbon dioxide provided a 90% recovery of polychlorobiphenyls from
sediments.
Gas chromatography
Gas chromatography has been used extensively for the determination of polychlorobiphenyls in river sediments [35, 37, 39–41, 124–126]. Both Capillary [35, 37, 123,
127] and packed [138–140, 125] have been used.
Brown et al [37] showed that agents capable of attacking polychlorinated
biphenyls might leave residues that exhibit characteristic signatures in the capillary gas
Chlorofluoromethane provided the highest recoveries while methanol modified carbon
dioxide gas 90% recovery of polychlorobiphenyls for sediments.
Herbert et al [122] used microwave-assisted extraction, combined with headspace
solid phase micro extraction and high resolution gas chromatography with ion-trap
tandem mass spectrometry to determine polychlorobiphenyls in sediments and soils.
Optimisation of the headspace solid phase micro extraction was carried out for the
most important parameters such as extraction time, sample volume and temperature.
The adopted methodology has reduced consumption of organic solvents and analysis
runtime. Under the optimised conditions, the method detection limit ranged from 0.6
to 1 ng/g when 5 g of sample was extracted, the precision on real samples ranged from
4 to 21% and the recovery from 69 to 104%. The proposed method, which included
the analysis of a certified reference material in its validation procedure, can be extended
to several other PCBs and used in the monitoring of soil or sediments for the presence
of PCBs.
Figure 6.3 shows the chromatographic separation of the selected PCBs in the
CP-Sil 8 analytical column obtained from a head space solid phase micro-extraction of
microwave assisted extracts from the CRM 536 (1 g extracted) and from a soil sample
(5 g extracted) collected in a landfill (42.8% humidity and 2.79% total organic matter
content).
The elution order obtained for PCBs compares to previously reported order for
PCBs within a homologue group on non-polar stationary phases according to the
number of ortho chlorines present.
Kominar et al [123] has described a method for the determination of polychlorobiphenyls in river sediments in which samples were extracted using ultrasonics into
1:1 n-hexane/acetone. The extract was partitioned with water and back extracted into
benzene. Combined organic extracts were dried on sodium sulphate, reduced in volume and cleaned up by gel permeation chromatography and silica gel partitioning.
Analysis of polychlorobiphenyls was carried out by gas chromatography with electron
capture detection.
Langenfeld et al [81, 133] studied the effect of temperature and pressure on
supercritical fluid efficiencies of polychlorinated biphenyls in river sediments. At a
temperature of 50
◦ C raising the pressure from 350 to 650 atmosphere had no beneficial effect on recovery of polychlorinated biphenyls from sediments. Recovery was
improved, however, as the extraction temperature was increased from 50
◦ C to 200
◦ C.
Langenfield et al [133] compared supercritical monochlorodifluoromethane,
nitrogen dioxide and carbon dioxide for the extraction of polychlorobiphenyls from
sediments. Monochlorodifluoromethane provided the highest recovery. Methanol
modified carbon dioxide provided a 90% recovery of polychlorobiphenyls from
sediments.
Gas chromatography
Gas chromatography has been used extensively for the determination of polychlorobiphenyls in river sediments [35, 37, 39–41, 124–126]. Both Capillary [35, 37, 123,
127] and packed [138–140, 125] have been used.
Brown et al [37] showed that agents capable of attacking polychlorinated
biphenyls might leave residues that exhibit characteristic signatures in the capillary gas