4
Introduction
ations apply in the case of some other elements and analytical methodology should
always be carefully checked out before a procedure is adopted. Thus results obtained
with anoxic estuarine and coastal sediments 609 have shown that attempts to dry samples
by oven drying or freeze drying prior to the determination of heavy metals gave
unreliable analyses as did storage methods involving aeration of the sample. Anoxic
sediments should be extracted with chemical leaching reagents under oxygen-free
conditions and a correction applied for separately determined volatiles content.
1.2
Determination of Organometallic Compounds
Some elements such as arsenic, antimony, bismuth, selenium, mercury, lead and tin
can exist in solid matter in both inorganic and organic forms. The organic forms of
the element may originate either by direct contamination of the solid by organic
compounds of industrial origin or by naturally occurring biomethylation processes
whereby inorganic forms of metals such as mercury and selenium are converted to the
organic form, for example, in fish tissues or in sediments. Suitable handling procedures both during sampling and analysis are necessary to avoid losses of metals in such
instances.
Several sample digestion techniques, some involving a subsequent extraction with
an organic solvent, have been described for the determination of organometallic
compounds in sediments, fish, crustacea and algae.
Successive extractions of the solid with 6 N hydrochloric acid and sodium hydroxide have been used to extract, respectively, total and organic arsenic from plankton
and sediments prior to analysis by spectroscopic or hydride generation atomic absorption spectrometric techniques. Aqueous sulphuric acid decomposition has also
been used in the case of organoarsenic compounds in fish and sulphuric-perchloric
acids or sulphuric-perchloric acids-hydrogen peroxide have been used in the case of
organomercury compounds in fish prior to analysis, respectively, by neutron activation analysis or atomic absorption spectrometry. Nitric-perchloric-hydrofluoric acid
mixtures have been used to decompose organotin compounds in sediments prior to
their determination by hydride generation atomic absorption spectrometry.
Digestion of fish with alkalies has been used to decompose organometallic compounds. Thus, organolead compounds have been digested with tetramethyl ammonium hydroxide prior to extraction with benzene and determination by gas chromatography. Organomercury compounds have been digested with sodium hydroxide prior
to extraction with toluene and determination by cold vapour atomic absorption
spectrometry, gas chromatography or high performance liquid chromatography. Direct solvent extraction with benzene, toluene or chloroform separates organolead and
organomercury compounds from sediments and fish prior to analysis by gas chromatography or column chromatography.
Combinations of digestion reagents and sediment extraction have also been used.
Thus, nitric acid digestion followed by hexane extraction separates organotin compounds from fish. Methanolic hydrochloric acid or ethereal tropalone separate organotin compounds from sediments prior to gas chromatographic analysis. Treatment
Introduction
ations apply in the case of some other elements and analytical methodology should
always be carefully checked out before a procedure is adopted. Thus results obtained
with anoxic estuarine and coastal sediments 609 have shown that attempts to dry samples
by oven drying or freeze drying prior to the determination of heavy metals gave
unreliable analyses as did storage methods involving aeration of the sample. Anoxic
sediments should be extracted with chemical leaching reagents under oxygen-free
conditions and a correction applied for separately determined volatiles content.
1.2
Determination of Organometallic Compounds
Some elements such as arsenic, antimony, bismuth, selenium, mercury, lead and tin
can exist in solid matter in both inorganic and organic forms. The organic forms of
the element may originate either by direct contamination of the solid by organic
compounds of industrial origin or by naturally occurring biomethylation processes
whereby inorganic forms of metals such as mercury and selenium are converted to the
organic form, for example, in fish tissues or in sediments. Suitable handling procedures both during sampling and analysis are necessary to avoid losses of metals in such
instances.
Several sample digestion techniques, some involving a subsequent extraction with
an organic solvent, have been described for the determination of organometallic
compounds in sediments, fish, crustacea and algae.
Successive extractions of the solid with 6 N hydrochloric acid and sodium hydroxide have been used to extract, respectively, total and organic arsenic from plankton
and sediments prior to analysis by spectroscopic or hydride generation atomic absorption spectrometric techniques. Aqueous sulphuric acid decomposition has also
been used in the case of organoarsenic compounds in fish and sulphuric-perchloric
acids or sulphuric-perchloric acids-hydrogen peroxide have been used in the case of
organomercury compounds in fish prior to analysis, respectively, by neutron activation analysis or atomic absorption spectrometry. Nitric-perchloric-hydrofluoric acid
mixtures have been used to decompose organotin compounds in sediments prior to
their determination by hydride generation atomic absorption spectrometry.
Digestion of fish with alkalies has been used to decompose organometallic compounds. Thus, organolead compounds have been digested with tetramethyl ammonium hydroxide prior to extraction with benzene and determination by gas chromatography. Organomercury compounds have been digested with sodium hydroxide prior
to extraction with toluene and determination by cold vapour atomic absorption
spectrometry, gas chromatography or high performance liquid chromatography. Direct solvent extraction with benzene, toluene or chloroform separates organolead and
organomercury compounds from sediments and fish prior to analysis by gas chromatography or column chromatography.
Combinations of digestion reagents and sediment extraction have also been used.
Thus, nitric acid digestion followed by hexane extraction separates organotin compounds from fish. Methanolic hydrochloric acid or ethereal tropalone separate organotin compounds from sediments prior to gas chromatographic analysis. Treatment