Organic compounds in sludges 233
of which is first shaken with 7% fuming sulphuric acid to remove lipids, and then
with cyanide to eliminate interference by elemental sulphur. The other aliquot is evaporated to dryness and heated with ethanolic potassium hydroxide. The two aliquots
are injected into a gas chromatograph fitted with a glass capillary column and an
electron capture detector. Hexabromobenzene is used as an internal standard. Polychlorinated biphenyls are determined quantitatively by comparing the peaks of the
sample with those of Clophen A50 or A60. The individual percentage composition of
the chlorobiphenyls in the polychlorinated biphenyl oils is used.
The concentration levels of chlorinated hydrocarbons in sewage sludge allowed the
use of a splitter injection technique. These impurities, together in the first part of the
column, cause poor separations and lower sensitivity. Nearly 70 peaks were detectable
when polychlorobiphenyl oil (Clophen A 50) was chromatographed. The polychlorobiphenyls are quantitated by using the percentage composition of the individual
compounds in the polychlorobiphenyl oils.
This method has good reproducibility and has a detection limit for the total amount
of polychlorobiphenyls in the dried sample of at least 0.1 mg kg
−1 and for DDT, DDD
and DDE limits of 0.01, 0.005 and 0.006 mg kg
−1 respectively.
Mattson and Nygren et al [153] point out that lipids and some other impurities
in the crude extracts of sewage sludge can be destroyed by treatment with fuming
sulphuric acid, either by shaking with the acid [159] or by eluting on a fuming sulphuric
acid-Celite column [160, 161]. Dieldrin is decomposed by this treatment but DDT and
its metabolites, DDD and DDE, are not extracts of sewage sludges often contain large
amounts of elemental sulphur, particularly after treatment with sulphuric acid. These
interfere with early eluting compound in the gas chromatographic step.
Sulphur was removed by the Bartless and Skoog et al [161] method in which the
sulphur is reacted with cyanide in acetone solution to produce thiocyanate. BGCs are
decomposed to some extent, probably to pentachlorocychlohexane. An alternative
procedure for the removal of sulphur utilising barium hydroxide is also described.
Alkali hydroxides should not be used as they cause dehydrochlorination of BHCs
[153]. Lindane and its isomers are dehydrochlorinated to trichlorobenzenes [162] and
are eluted together with the solvent. Mattsson and Nygren et al [153] have also tested
a column with a packed alkaline post-column to remove the sulphur peak from the
chromatograph. In the post-column DDT and DDD are dehydroclorinated but this
does not affect their retention times. Cochrane and Maybury et al [163] have used the
reaction with sodium hydroxide in methanol for the identification of BHCs. Dieldrin
is not decomposed in the potassium hydroxide treatment and can thus be detected in
the chromatogram of the aliquot.
McIntyre et al [154, 155] described a method for the analysis of polychlorobiphenyls and chlorinated insecticides in sewage sludges in which homogenised samples
are extracted with hexane, concentrated and cleaned up on an alumina/alumina plus
sliver nitrate column and eluted with hexane. After concentration of the eluent,
polychlorobiphenyl and organochlorine compounds were determined by a silica gel
chromatographic procedure and gas chromatography.
McIntyre et al [154, 155] found that the silica gel chromatographic method of
Holden and Marsden et al [164] resulted in good reproducible separation of polychlorobiphenyls and organochlorine insecticides. Polychlorobiphenyls and DDE were
found to emerge in the first 6 ml of hexane eluate, while the remaining organochlorine
of which is first shaken with 7% fuming sulphuric acid to remove lipids, and then
with cyanide to eliminate interference by elemental sulphur. The other aliquot is evaporated to dryness and heated with ethanolic potassium hydroxide. The two aliquots
are injected into a gas chromatograph fitted with a glass capillary column and an
electron capture detector. Hexabromobenzene is used as an internal standard. Polychlorinated biphenyls are determined quantitatively by comparing the peaks of the
sample with those of Clophen A50 or A60. The individual percentage composition of
the chlorobiphenyls in the polychlorinated biphenyl oils is used.
The concentration levels of chlorinated hydrocarbons in sewage sludge allowed the
use of a splitter injection technique. These impurities, together in the first part of the
column, cause poor separations and lower sensitivity. Nearly 70 peaks were detectable
when polychlorobiphenyl oil (Clophen A 50) was chromatographed. The polychlorobiphenyls are quantitated by using the percentage composition of the individual
compounds in the polychlorobiphenyl oils.
This method has good reproducibility and has a detection limit for the total amount
of polychlorobiphenyls in the dried sample of at least 0.1 mg kg
−1 and for DDT, DDD
and DDE limits of 0.01, 0.005 and 0.006 mg kg
−1 respectively.
Mattson and Nygren et al [153] point out that lipids and some other impurities
in the crude extracts of sewage sludge can be destroyed by treatment with fuming
sulphuric acid, either by shaking with the acid [159] or by eluting on a fuming sulphuric
acid-Celite column [160, 161]. Dieldrin is decomposed by this treatment but DDT and
its metabolites, DDD and DDE, are not extracts of sewage sludges often contain large
amounts of elemental sulphur, particularly after treatment with sulphuric acid. These
interfere with early eluting compound in the gas chromatographic step.
Sulphur was removed by the Bartless and Skoog et al [161] method in which the
sulphur is reacted with cyanide in acetone solution to produce thiocyanate. BGCs are
decomposed to some extent, probably to pentachlorocychlohexane. An alternative
procedure for the removal of sulphur utilising barium hydroxide is also described.
Alkali hydroxides should not be used as they cause dehydrochlorination of BHCs
[153]. Lindane and its isomers are dehydrochlorinated to trichlorobenzenes [162] and
are eluted together with the solvent. Mattsson and Nygren et al [153] have also tested
a column with a packed alkaline post-column to remove the sulphur peak from the
chromatograph. In the post-column DDT and DDD are dehydroclorinated but this
does not affect their retention times. Cochrane and Maybury et al [163] have used the
reaction with sodium hydroxide in methanol for the identification of BHCs. Dieldrin
is not decomposed in the potassium hydroxide treatment and can thus be detected in
the chromatogram of the aliquot.
McIntyre et al [154, 155] described a method for the analysis of polychlorobiphenyls and chlorinated insecticides in sewage sludges in which homogenised samples
are extracted with hexane, concentrated and cleaned up on an alumina/alumina plus
sliver nitrate column and eluted with hexane. After concentration of the eluent,
polychlorobiphenyl and organochlorine compounds were determined by a silica gel
chromatographic procedure and gas chromatography.
McIntyre et al [154, 155] found that the silica gel chromatographic method of
Holden and Marsden et al [164] resulted in good reproducible separation of polychlorobiphenyls and organochlorine insecticides. Polychlorobiphenyls and DDE were
found to emerge in the first 6 ml of hexane eluate, while the remaining organochlorine