7.4
Organometallic Compounds
7.4.7
Arsenic
Organometallic Compounds
161
Fishman and Spencer [490] used an ultraviolet radiation or an acid persulphate
digestion procedure to decompose organoarsenic compounds. The automated methods of Agemian and Cheam [491] use hydrogen peroxide and sulphuric acid for the
destruction of organic matter, combined with permanganate-persulphate oxidation
for the complete recovery of organoarsenic compounds from fish. An automated
system based on sodium borohydride reduction with atomization in a quartz tube is
used for the determination of the inorganic arsenic thus produced.
Agemian and Cheam [491] found that, in the sodium borohydride reduction of
inorganic arsenic to arsenic, concentrations from 0.5 to 1.5 mol I-I of hydrochloric acid
gave the highest sensitivity; both As(III) and As(V) were equivalently detected. When
the hydrochloric acid concentration was increased from 2 to 6 mol I-I , the sensitivity for
both species decreased, particularly for As(V). Replacement of the hydrochloric acid
line with a sulphuric acid line reduced the sensitivity for As(III) by about 30 %, and
As(V) gave a sensitivity of about 50 % As(III). Replicate determinations at a level of
0.10 Ilg As g-I in a fish sample gave a relative standard deviation of 15 %.
Maher [492] has described a method for determining inorganic arsenic, mono methylarsenic, acid and dimethylarsinic acid in fish. The procedure involves the use of
solvent extraction to isolate the arsenic species which are then separated by ionexchange chromatography, and determined by arsine generation.
Beauchemin et al. [758] identified and determined organic arsenic species in a
dogfish muscle reference sample using high performance liquid chromatography
coupled with inductivly coupled plasma - mass spectrometry, thin-layer chromatography and electron impact mass spectrometry - graphite furnace atomic absorption
spectrometry. The major species (84 % of total arsenic) was arseno betaine, present at
161lg g-I (as arsenic) in the dogfish sample.
7.4.2
Lead
Chau et al. [493] have described a simple and rapid extraction procedure to extract the
five tetraalkyllead compounds (Me 4 Pb, Me 3 EtPb, MezEtzPb, MeEt 3 Pb, and Etlb) from
fish samples. The extracted compounds are analysed in their authentic forms by a gas
chromatographic-atomic adsorption spectrometry system. Other forms of inorganic
lead do not interfere. The detection limits for water and fish (2 g) was 0.025 mg kg-I.
The recovery of the five alkylated lead compounds from fish tissue averaged 74 % and
the coefficient of variation 7.4 %. Whilst this method would be applicable to the
determination of tetraalkyllead compounds in fish, the main interest of Chau et al.
was in the determination of organically bound lead produced by biological methylation of inorganic and organic lead compounds in the aquatic environment by microorganisms [493]. The gas chromatographic-atomic absorption system used by
Chau et al. (used without a sample injection trap) for this procedure has been
Organometallic Compounds
7.4.7
Arsenic
Organometallic Compounds
161
Fishman and Spencer [490] used an ultraviolet radiation or an acid persulphate
digestion procedure to decompose organoarsenic compounds. The automated methods of Agemian and Cheam [491] use hydrogen peroxide and sulphuric acid for the
destruction of organic matter, combined with permanganate-persulphate oxidation
for the complete recovery of organoarsenic compounds from fish. An automated
system based on sodium borohydride reduction with atomization in a quartz tube is
used for the determination of the inorganic arsenic thus produced.
Agemian and Cheam [491] found that, in the sodium borohydride reduction of
inorganic arsenic to arsenic, concentrations from 0.5 to 1.5 mol I-I of hydrochloric acid
gave the highest sensitivity; both As(III) and As(V) were equivalently detected. When
the hydrochloric acid concentration was increased from 2 to 6 mol I-I , the sensitivity for
both species decreased, particularly for As(V). Replacement of the hydrochloric acid
line with a sulphuric acid line reduced the sensitivity for As(III) by about 30 %, and
As(V) gave a sensitivity of about 50 % As(III). Replicate determinations at a level of
0.10 Ilg As g-I in a fish sample gave a relative standard deviation of 15 %.
Maher [492] has described a method for determining inorganic arsenic, mono methylarsenic, acid and dimethylarsinic acid in fish. The procedure involves the use of
solvent extraction to isolate the arsenic species which are then separated by ionexchange chromatography, and determined by arsine generation.
Beauchemin et al. [758] identified and determined organic arsenic species in a
dogfish muscle reference sample using high performance liquid chromatography
coupled with inductivly coupled plasma - mass spectrometry, thin-layer chromatography and electron impact mass spectrometry - graphite furnace atomic absorption
spectrometry. The major species (84 % of total arsenic) was arseno betaine, present at
161lg g-I (as arsenic) in the dogfish sample.
7.4.2
Lead
Chau et al. [493] have described a simple and rapid extraction procedure to extract the
five tetraalkyllead compounds (Me 4 Pb, Me 3 EtPb, MezEtzPb, MeEt 3 Pb, and Etlb) from
fish samples. The extracted compounds are analysed in their authentic forms by a gas
chromatographic-atomic adsorption spectrometry system. Other forms of inorganic
lead do not interfere. The detection limits for water and fish (2 g) was 0.025 mg kg-I.
The recovery of the five alkylated lead compounds from fish tissue averaged 74 % and
the coefficient of variation 7.4 %. Whilst this method would be applicable to the
determination of tetraalkyllead compounds in fish, the main interest of Chau et al.
was in the determination of organically bound lead produced by biological methylation of inorganic and organic lead compounds in the aquatic environment by microorganisms [493]. The gas chromatographic-atomic absorption system used by
Chau et al. (used without a sample injection trap) for this procedure has been