Determination of Organic Compounds
5
with sodium iodide, hydrobromic acid or acidic cupric bromide followed by toluene
or hexane extraction isolates organomercury compounds from fish and sediments
prior to gas chromatographic or atomic absorption spectrometric analysis. Other
decomposition procedures for organometallic compounds utilise aqueous EDT A (organolead compounds in fish and sediments), enzymic degradation followed by toluene extraction (organomercury compounds in fish), bomb digestion under oxygen
(organomercury compounds in sediments) and digestion with borate buffered sodium borohydride followed by hydride generation atomic absorption spectrometry
(organotin compounds in sediments).
1.3
Determination of Organic Compounds
Various procedures have been used to isolate organic compounds from sediments,
fish, crustacea and algae preparatory to analysis. The simplest method is direct
solvent extraction. Various solvents have been used - n-hexane extracts hydrocarbons, chlorophenols and chlorinated insecticides from sediments prior to analysis by
gas chromatography. Benzene also extracts hydrocarbons from sediments. Methanol
and acetone extract chlorophylls from algae prior to spectroscopy, thin-layer chromatography or high performance liquid chromatography - methylene dichloride extracts alkyl phosphates, organophosphorus insecticides and herbicides from sediments, and separates polyaromatic hydrocarbons from fish prior to gas chromatography. Petroleum ether and hexane-acetone are useful for the extraction of non-volatile
chloro compounds, chlorinated insecticides and polychlorinated biphenyls from sediments and crustacea. Acetonitrile or acetonitrile followed by methylene dichloride
and petroleum ether are useful solvents for isolating miscellaneous unknown organic
compounds from fish and sediments, prior to examination by gas chromatography
and mass spectrometry to achieve definitive identifications.
A further refinement is to reflux the sample with an acid or alkali and then solvent
extract the degradation products for identification. Thus treatment of fish with
sulphuric acid followed by extraction with isopropanol-hexane enables chlorophenols, chlorinated insecticides and polychlorostyrenes to be determined by gas chromatography. Fuming sulphuric acid treatment followed by hexane extraction facilitates the determination of chlorinated insecticides in algae.
Reflux with alcoholic potassium hydroxide followed by solvent extraction enables
hydrocarbons, polyaromatic hydrocarbons and dioxins to be determined gas chromatographically in extracts of fish, sediments and crustacea.
Other isolation techniques that have been used for organics include flash pyrolysisgas chromatography-mass spectrometry for the determination of polyaromatic hydrocarbons and polychlorinated biphenyls in sediments, headspace analysis-gas chromatography-mass spectrometry for the determination of hydrocarbons and volatile chIoro
compounds in sediments and miscellaneous organics in algae, and steam distillation for
the determination of non-volatile chlorocompounds in sediments and fish.
A detailed discussion of the various techniques available for the analysis of solid
materials from water follows in Chaps. 2-10.
5
with sodium iodide, hydrobromic acid or acidic cupric bromide followed by toluene
or hexane extraction isolates organomercury compounds from fish and sediments
prior to gas chromatographic or atomic absorption spectrometric analysis. Other
decomposition procedures for organometallic compounds utilise aqueous EDT A (organolead compounds in fish and sediments), enzymic degradation followed by toluene extraction (organomercury compounds in fish), bomb digestion under oxygen
(organomercury compounds in sediments) and digestion with borate buffered sodium borohydride followed by hydride generation atomic absorption spectrometry
(organotin compounds in sediments).
1.3
Determination of Organic Compounds
Various procedures have been used to isolate organic compounds from sediments,
fish, crustacea and algae preparatory to analysis. The simplest method is direct
solvent extraction. Various solvents have been used - n-hexane extracts hydrocarbons, chlorophenols and chlorinated insecticides from sediments prior to analysis by
gas chromatography. Benzene also extracts hydrocarbons from sediments. Methanol
and acetone extract chlorophylls from algae prior to spectroscopy, thin-layer chromatography or high performance liquid chromatography - methylene dichloride extracts alkyl phosphates, organophosphorus insecticides and herbicides from sediments, and separates polyaromatic hydrocarbons from fish prior to gas chromatography. Petroleum ether and hexane-acetone are useful for the extraction of non-volatile
chloro compounds, chlorinated insecticides and polychlorinated biphenyls from sediments and crustacea. Acetonitrile or acetonitrile followed by methylene dichloride
and petroleum ether are useful solvents for isolating miscellaneous unknown organic
compounds from fish and sediments, prior to examination by gas chromatography
and mass spectrometry to achieve definitive identifications.
A further refinement is to reflux the sample with an acid or alkali and then solvent
extract the degradation products for identification. Thus treatment of fish with
sulphuric acid followed by extraction with isopropanol-hexane enables chlorophenols, chlorinated insecticides and polychlorostyrenes to be determined by gas chromatography. Fuming sulphuric acid treatment followed by hexane extraction facilitates the determination of chlorinated insecticides in algae.
Reflux with alcoholic potassium hydroxide followed by solvent extraction enables
hydrocarbons, polyaromatic hydrocarbons and dioxins to be determined gas chromatographically in extracts of fish, sediments and crustacea.
Other isolation techniques that have been used for organics include flash pyrolysisgas chromatography-mass spectrometry for the determination of polyaromatic hydrocarbons and polychlorinated biphenyls in sediments, headspace analysis-gas chromatography-mass spectrometry for the determination of hydrocarbons and volatile chIoro
compounds in sediments and miscellaneous organics in algae, and steam distillation for
the determination of non-volatile chlorocompounds in sediments and fish.
A detailed discussion of the various techniques available for the analysis of solid
materials from water follows in Chaps. 2-10.