102 Organic compounds in soils, sediments & sludges
sensitivity. The yield of ester from the acid-catalysed reaction of acid and alcohol,
although reproducible, is usually of the order of only 80%. Pentafluorobenzylation
and alkali metal carbonate-catalysed alkylation require anhydrous conditions. The use
of halogenated reagents also has the disadvantage of transferring electron-capturing
properties to impurities or coextractants that may interfere with measurement of the
herbicide. Extractive or ion-pair alkylation is an alternative method that has been
reported [300–303].
This layer chromatography
Abbott and Wagstaff et al [304] have described a thin layer chromatographic method
for the identification of 12 acidic herbicides and 19 nitrogenous herbicides (carbamates,
substituted ureas and triazine).
Smith and Fitzpatrick et al [305] have also described a thin layer method for
the detection in water and soil of herbicide residues, including Atrazine, Barban,
Diuron, Linuron, Monuron, Simazine, Trifluralin, Bromoxynil, Dalapon, Dicamba,
MCPB, Mecoprop, Dicloram, 2,4-D, 2,4-DB, Dichloroprop, 2,4,5-T, and 2,3,6trichlorobenzoic acid.
Neutral and basic herbicides were extracted from soil with chloroform; extracts of
soil were cleaned up on basic alumina containing 15% of water. Acidic herbicides were
extracted with ethyl ether from an aqueous extract of soil prepared by treatment with
10% aqueous potassium chloride that was 0.05M in sodium hydroxide and filtration
into 4M hydrochloric acid. The concentrated chloroform solution of neutral and basic
herbicides was applied to a pre-coated silica gel plate containing a fluorescent indicator
and a chromatogram was developed two-dimensionally with hexane-acetone (10:3)
followed after drying by chloroform-nitromethane (1:1). The spots were detected in
UV radiation. Atrazine, Barban, Diuron, Linuron, Monuron, Simazine and Trifluralin
were successfully separated and were located as purple spots on a green fluorescent
background. The ether extracts were dried over sodium sulphate, concentrated, and
applied to a similar plate, which was developed two-dimensionally with chloroformanhydrous acetic acid (19:1) followed after drying by benzene-hexane-anhydrous acetic
acid (5:10:2). The spots were detected by spraying with bromocresol green. Bromoxynil
and (as the acids) Dalapon, Dicamba, MCPA, MCPB, Mecoprop, Dicloram, 2,4-DB,
Dichloroprop, 2,4,5-T and 2,3,6-trichlorobenzoic acid were seen as yellow spots on a
blur background.
Supercritical fluid chromatography
Snyder et al [6] compared supercritical fluid chromatography with classical sonication procedures and Soxhlet extraction for the determination of selected insecticides in soils and sediments. In this procedure the sample was extracted with
carbon dioxide modified with 3% methanol at 350 atm and 50
◦ C. An excess of
85% recovery of organochlorine and organophosphorus insecticides was achieved.
These included Dichlorvos, Diazinon, (diethyl-2-isopropyl-6-methyl 4-pyrimidinyl
phosphorothioate), Ronnel (i.e. Fenchlorphos-O,O, dimethyl-O-2,4,5-trichlorophenyl
phosphorothioate), Parathion ethyl, Methiadathion, Tetrachlorovinphos (trans-2chloro-1-(2,4,5 trichlorophenyl) vinylchlorophenyl-O-methyl phenyl phosphoroamidothioate), Endrin, Endrin aldehyde, pp’ DDT, Mirex and decachlorobiphenyl.
sensitivity. The yield of ester from the acid-catalysed reaction of acid and alcohol,
although reproducible, is usually of the order of only 80%. Pentafluorobenzylation
and alkali metal carbonate-catalysed alkylation require anhydrous conditions. The use
of halogenated reagents also has the disadvantage of transferring electron-capturing
properties to impurities or coextractants that may interfere with measurement of the
herbicide. Extractive or ion-pair alkylation is an alternative method that has been
reported [300–303].
This layer chromatography
Abbott and Wagstaff et al [304] have described a thin layer chromatographic method
for the identification of 12 acidic herbicides and 19 nitrogenous herbicides (carbamates,
substituted ureas and triazine).
Smith and Fitzpatrick et al [305] have also described a thin layer method for
the detection in water and soil of herbicide residues, including Atrazine, Barban,
Diuron, Linuron, Monuron, Simazine, Trifluralin, Bromoxynil, Dalapon, Dicamba,
MCPB, Mecoprop, Dicloram, 2,4-D, 2,4-DB, Dichloroprop, 2,4,5-T, and 2,3,6trichlorobenzoic acid.
Neutral and basic herbicides were extracted from soil with chloroform; extracts of
soil were cleaned up on basic alumina containing 15% of water. Acidic herbicides were
extracted with ethyl ether from an aqueous extract of soil prepared by treatment with
10% aqueous potassium chloride that was 0.05M in sodium hydroxide and filtration
into 4M hydrochloric acid. The concentrated chloroform solution of neutral and basic
herbicides was applied to a pre-coated silica gel plate containing a fluorescent indicator
and a chromatogram was developed two-dimensionally with hexane-acetone (10:3)
followed after drying by chloroform-nitromethane (1:1). The spots were detected in
UV radiation. Atrazine, Barban, Diuron, Linuron, Monuron, Simazine and Trifluralin
were successfully separated and were located as purple spots on a green fluorescent
background. The ether extracts were dried over sodium sulphate, concentrated, and
applied to a similar plate, which was developed two-dimensionally with chloroformanhydrous acetic acid (19:1) followed after drying by benzene-hexane-anhydrous acetic
acid (5:10:2). The spots were detected by spraying with bromocresol green. Bromoxynil
and (as the acids) Dalapon, Dicamba, MCPA, MCPB, Mecoprop, Dicloram, 2,4-DB,
Dichloroprop, 2,4,5-T and 2,3,6-trichlorobenzoic acid were seen as yellow spots on a
blur background.
Supercritical fluid chromatography
Snyder et al [6] compared supercritical fluid chromatography with classical sonication procedures and Soxhlet extraction for the determination of selected insecticides in soils and sediments. In this procedure the sample was extracted with
carbon dioxide modified with 3% methanol at 350 atm and 50
◦ C. An excess of
85% recovery of organochlorine and organophosphorus insecticides was achieved.
These included Dichlorvos, Diazinon, (diethyl-2-isopropyl-6-methyl 4-pyrimidinyl
phosphorothioate), Ronnel (i.e. Fenchlorphos-O,O, dimethyl-O-2,4,5-trichlorophenyl
phosphorothioate), Parathion ethyl, Methiadathion, Tetrachlorovinphos (trans-2chloro-1-(2,4,5 trichlorophenyl) vinylchlorophenyl-O-methyl phenyl phosphoroamidothioate), Endrin, Endrin aldehyde, pp’ DDT, Mirex and decachlorobiphenyl.