144 Organic compounds in soils, sediments & sludges
with gas chromatography to study the formation of chlorinated aliphatics during the
chlorination of waste waters. Chlorinated normal paraffins up to the C 30 carbon number range are of low volatility and are thermally unstable, producing hydrogen chloride
on decomposition; hence direct gas chromatography is not attractive.
Gas chromatography-mass spectrometry
Gas chromatography-mass spectrometry has been applied to the determination of
volatiles in river sediment samples [21].
Carey and Hart et al [116] collected samples of ‘pools’ of non-aqueous material on
the surface of sediments in the St. Clair river, Ontario, and analysed by gas chromatography and mass spectrometry. A large number of compounds were identified including
tetrachloroethane, tetra-, penta- and hexachloroethanes, chlorobutanes, chlorobutadienes, chlorohexadienes, heptachlorostyrene, octachlorostyrene and octachloronaphthalene. The results suggested that the source of the pools was not just a simple spill
of perchlorethylene, as previously thought.
Purge and trap gas chromatography
Charles and Simons et al [22] obtained overall recoveries of 38% and 48% and 54%
respectively, for chloroform, trichloroethylene and chlorobenzenes from sediments
using purge and trap methods.
Column chromatography
Zitko et al [117] has devised a method based on column chromatography followed by
microcoulmometric detection. The procedure is not specific.
Thin layer chromatography
Hollies et al [118] have carried out an extensive study of the determination of chlorinated long chain (C 13 –C 20 ) normal paraffins (Cerechlors) in river sediments. They
considered liquid chromatography, gas chromatography and thin layer chromatography. Chlorinated paraffins are separated from the sediment by Soxhlet extraction
with petroleum ether. A concentrate of the extract is then cleaned up on an alumina
column which adsorbs these compounds, allowing impurities to pass through. The
chlorinated paraffins are then desorbed with toluene. Analysis of the extracts is carried out by thin-layer chromatography on silica. The plate is developed by covering
with a second plate coated with alumina and heating face to face at 240
◦ C. The alumina plate is then sprayed with silver nitrate to visualise the separated chloroparaffins
as grey-black spots. Any chloroparaffins present in the extract are then identified by
reference to the R, values which are approximately 0.74 and 0.80 for C 13 –C 17 and
C 20 –C 30 chloroparaffins respectively.
6.3.2 Non-volatile aliphatic chlorohydrocarbons
Chlorinated hydrocarbons that have been determined in extracts of river sediments
by gas chromatography include higher chlorinated aromatic hydrocarbons and polychlorobiphenyls. Hawthorne et al [121] compared supercritical chlorophenols, nitrous
oxide and carbon dioxide for the extraction of polychlorobiphenyls from sediments.
with gas chromatography to study the formation of chlorinated aliphatics during the
chlorination of waste waters. Chlorinated normal paraffins up to the C 30 carbon number range are of low volatility and are thermally unstable, producing hydrogen chloride
on decomposition; hence direct gas chromatography is not attractive.
Gas chromatography-mass spectrometry
Gas chromatography-mass spectrometry has been applied to the determination of
volatiles in river sediment samples [21].
Carey and Hart et al [116] collected samples of ‘pools’ of non-aqueous material on
the surface of sediments in the St. Clair river, Ontario, and analysed by gas chromatography and mass spectrometry. A large number of compounds were identified including
tetrachloroethane, tetra-, penta- and hexachloroethanes, chlorobutanes, chlorobutadienes, chlorohexadienes, heptachlorostyrene, octachlorostyrene and octachloronaphthalene. The results suggested that the source of the pools was not just a simple spill
of perchlorethylene, as previously thought.
Purge and trap gas chromatography
Charles and Simons et al [22] obtained overall recoveries of 38% and 48% and 54%
respectively, for chloroform, trichloroethylene and chlorobenzenes from sediments
using purge and trap methods.
Column chromatography
Zitko et al [117] has devised a method based on column chromatography followed by
microcoulmometric detection. The procedure is not specific.
Thin layer chromatography
Hollies et al [118] have carried out an extensive study of the determination of chlorinated long chain (C 13 –C 20 ) normal paraffins (Cerechlors) in river sediments. They
considered liquid chromatography, gas chromatography and thin layer chromatography. Chlorinated paraffins are separated from the sediment by Soxhlet extraction
with petroleum ether. A concentrate of the extract is then cleaned up on an alumina
column which adsorbs these compounds, allowing impurities to pass through. The
chlorinated paraffins are then desorbed with toluene. Analysis of the extracts is carried out by thin-layer chromatography on silica. The plate is developed by covering
with a second plate coated with alumina and heating face to face at 240
◦ C. The alumina plate is then sprayed with silver nitrate to visualise the separated chloroparaffins
as grey-black spots. Any chloroparaffins present in the extract are then identified by
reference to the R, values which are approximately 0.74 and 0.80 for C 13 –C 17 and
C 20 –C 30 chloroparaffins respectively.
6.3.2 Non-volatile aliphatic chlorohydrocarbons
Chlorinated hydrocarbons that have been determined in extracts of river sediments
by gas chromatography include higher chlorinated aromatic hydrocarbons and polychlorobiphenyls. Hawthorne et al [121] compared supercritical chlorophenols, nitrous
oxide and carbon dioxide for the extraction of polychlorobiphenyls from sediments.