158 Organic compounds in soils, sediments & sludges
Mills and Thurmen et al [193] used a mixed method for the isolation of triazine
herbicide metabolites from aquifer sediments using automated solid phases extraction with a mixture of methanol and water (4:1 V/V). Following evaporation of the
methanol phases, the metabolites were collected in a column of C18 octadecyl resin.
The analytes were then stripped from the column with ethyl acetate leaving impurities
on the column. Down to 0.1 µg kg
−1 triazine could be determined.
Tang et al [194] discussed the determination of Atrazine and its deethylated degradation product in sediment using gas chromatography ion trap mass spectrometry.
The isotope dilution technique was applied for the quantitative analyses of
Atrazine at parts-per-trillion levels. Water samples were pre-concentrated by solidphase extraction using a C18 cartridge while the sediment samples were extracted
by sonication with methanol. The concentrated extracts were analysed by a GC/ion
trap MS operated in the MS/MS method. The extraction recoveries for the analytes
were better than 83% when 1 litre of water or 10 g of sediment was analysed. The
method detection limits were 0.75% ng/L and 0.13 ng/g for Atrazine and deethylatrazine detected in water and sediment, respectively. The precisions of the method
represented by the relative standard deviation were in the range of 3.2–16.1%. The
method was successfully applied to analyse surface water and sediment samples collected from Beijing Guanting reservoir. Trace levels of Atrazine at 35.9–217.3 ng/L and
2.4–8.4 ng/g were detected in the water and sediment samples, respectively. The levels
of deethylatrazine were five to 20 times lower than those of Atrazine.
6.7.4 Carbamate type herbicides
Reeves and Woodham et al [148] have described a gas chromatographic method for
the determination of Methomyl (S-methyl-N-(methyl carbamoyl)oxy thioacetimidate)
insecticide in sediments. The residues were extracted with dichloromethane, and the
extracts were purified on a column of Florisil. The purified and concentrated extracts
were then examined by gas chromatography. The limits of detection were 0.5 mg kg
−1
and the recoveries were 91%.
Spengler and Jumar et al [195] used a spectrophotometric method and thin layer
chromatography to determined carbamate and urea herbicide residues in sediments.
The sample is extracted with acetone, the extract is evaporated in vacuo at 40
◦ C and
the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15%
aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam
distilled and collected in hydrochloric acid. The amine is diazotised and coupled with
thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the
azo-dye is determined spectrophotometrically at 440 nm (465 nm for the dye derived
from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent
blank.
6.7.5 Phenoxy acetic acid type herbicides
Kim et al [196] determined chlorinated phenoxy and ester herbicides in sediments at
the mg k
−1 level using particle beam mass spectrometry in conjunction with liquid
chromatography.
Mills and Thurmen et al [193] used a mixed method for the isolation of triazine
herbicide metabolites from aquifer sediments using automated solid phases extraction with a mixture of methanol and water (4:1 V/V). Following evaporation of the
methanol phases, the metabolites were collected in a column of C18 octadecyl resin.
The analytes were then stripped from the column with ethyl acetate leaving impurities
on the column. Down to 0.1 µg kg
−1 triazine could be determined.
Tang et al [194] discussed the determination of Atrazine and its deethylated degradation product in sediment using gas chromatography ion trap mass spectrometry.
The isotope dilution technique was applied for the quantitative analyses of
Atrazine at parts-per-trillion levels. Water samples were pre-concentrated by solidphase extraction using a C18 cartridge while the sediment samples were extracted
by sonication with methanol. The concentrated extracts were analysed by a GC/ion
trap MS operated in the MS/MS method. The extraction recoveries for the analytes
were better than 83% when 1 litre of water or 10 g of sediment was analysed. The
method detection limits were 0.75% ng/L and 0.13 ng/g for Atrazine and deethylatrazine detected in water and sediment, respectively. The precisions of the method
represented by the relative standard deviation were in the range of 3.2–16.1%. The
method was successfully applied to analyse surface water and sediment samples collected from Beijing Guanting reservoir. Trace levels of Atrazine at 35.9–217.3 ng/L and
2.4–8.4 ng/g were detected in the water and sediment samples, respectively. The levels
of deethylatrazine were five to 20 times lower than those of Atrazine.
6.7.4 Carbamate type herbicides
Reeves and Woodham et al [148] have described a gas chromatographic method for
the determination of Methomyl (S-methyl-N-(methyl carbamoyl)oxy thioacetimidate)
insecticide in sediments. The residues were extracted with dichloromethane, and the
extracts were purified on a column of Florisil. The purified and concentrated extracts
were then examined by gas chromatography. The limits of detection were 0.5 mg kg
−1
and the recoveries were 91%.
Spengler and Jumar et al [195] used a spectrophotometric method and thin layer
chromatography to determined carbamate and urea herbicide residues in sediments.
The sample is extracted with acetone, the extract is evaporated in vacuo at 40
◦ C and
the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15%
aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam
distilled and collected in hydrochloric acid. The amine is diazotised and coupled with
thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the
azo-dye is determined spectrophotometrically at 440 nm (465 nm for the dye derived
from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent
blank.
6.7.5 Phenoxy acetic acid type herbicides
Kim et al [196] determined chlorinated phenoxy and ester herbicides in sediments at
the mg k
−1 level using particle beam mass spectrometry in conjunction with liquid
chromatography.