Chapter 9
Organometallic compounds
in saline sediments
9.1 ORGANOARSENIC COMPOUNDS
The adsorption of organoarsenic compounds onto sediments under saline conditions
varies with the species of organoarsenic compound involved. It has been shown [1]
that inorganic arsenic (III and V); monomethylarsenic and dimethylarsenic acids are
present in natural waters [2, 6] and sediments [3, 4]. Thus analytical methods for the
separation and measurement of these species are necessary for the study of pathways
of accumulation and deposition.
Maher et al [5] has described a method for the determination of down to
0.01 mg/kg of organoarsenic compounds in marine sediments. In this procedure,
the organoarsenic compounds are separated from an extract of the sediment by ion
exchange chromatography, and the isolated organoarsenic compounds are reduced to
arsines with sodium borohydride and collected in a cold trap. Controlled evaporation
of the arsine fractions and detection by atomic absorption spectrometry completes the
analysis.
9.2 ORGANOLEAD COMPOUNDS
Chau et al [7] described a hexane extraction procedure to extract tetramethyllead,
trimethylethyllead methyltriethyl lead, dimethyldiethyl lead and tetraethyl lead from
marine sediments. The extracted compounds were analysed in their authentic forms
by a gas chromatographic-atomic absorption spectrometric system. Other forms of
organic and inorganic lead do not interfere. The detection limit was 0.01 mg kg
−1
as lead.
To digest sediment samples 5 g of sediment and EDTA solution are extracted with
5 ml hexane and the resulting solution gas chromatographed. Concentrations found
in a marine sediment ranged from 8.3 mg kg
−1 (tetramethyllead and methyltriethyllead) to 12 mg kg (dimethyldiethyllead and tetraethyllead) and recoveries in spiking
experiments were between 81 and 84%. Down to 0.01 mg kg
−1 organolead can be
determined by this method.
Chau et al [8] have described a simple and rapid extraction procedure to extract the
five tetraalkyllead compounds (Me 4 Pb, Me 3 , EtPb, Me 2 Et 2 Pb, MeEt 3 Pb and Et 4 Pb)
from sediment. The extracted compounds are analysed in their authentic form by gas
chromatography-atomic absorption spectrometry.
Organometallic compounds
in saline sediments
9.1 ORGANOARSENIC COMPOUNDS
The adsorption of organoarsenic compounds onto sediments under saline conditions
varies with the species of organoarsenic compound involved. It has been shown [1]
that inorganic arsenic (III and V); monomethylarsenic and dimethylarsenic acids are
present in natural waters [2, 6] and sediments [3, 4]. Thus analytical methods for the
separation and measurement of these species are necessary for the study of pathways
of accumulation and deposition.
Maher et al [5] has described a method for the determination of down to
0.01 mg/kg of organoarsenic compounds in marine sediments. In this procedure,
the organoarsenic compounds are separated from an extract of the sediment by ion
exchange chromatography, and the isolated organoarsenic compounds are reduced to
arsines with sodium borohydride and collected in a cold trap. Controlled evaporation
of the arsine fractions and detection by atomic absorption spectrometry completes the
analysis.
9.2 ORGANOLEAD COMPOUNDS
Chau et al [7] described a hexane extraction procedure to extract tetramethyllead,
trimethylethyllead methyltriethyl lead, dimethyldiethyl lead and tetraethyl lead from
marine sediments. The extracted compounds were analysed in their authentic forms
by a gas chromatographic-atomic absorption spectrometric system. Other forms of
organic and inorganic lead do not interfere. The detection limit was 0.01 mg kg
−1
as lead.
To digest sediment samples 5 g of sediment and EDTA solution are extracted with
5 ml hexane and the resulting solution gas chromatographed. Concentrations found
in a marine sediment ranged from 8.3 mg kg
−1 (tetramethyllead and methyltriethyllead) to 12 mg kg (dimethyldiethyllead and tetraethyllead) and recoveries in spiking
experiments were between 81 and 84%. Down to 0.01 mg kg
−1 organolead can be
determined by this method.
Chau et al [8] have described a simple and rapid extraction procedure to extract the
five tetraalkyllead compounds (Me 4 Pb, Me 3 , EtPb, Me 2 Et 2 Pb, MeEt 3 Pb and Et 4 Pb)
from sediment. The extracted compounds are analysed in their authentic form by gas
chromatography-atomic absorption spectrometry.