162
Fish
described [494]. The extract was injected directly into the column injection port of the
chromatograph. In this method, the frozen fish tissue was homogenized in a Hobart
grinder and a Polytron homogenizer and 2 g of the fish homogenated with 5 ml of
EDT A reagent, and 5 ml of hexane were immediately placed in a 25 ml test tube with a
Teflon lined screw cap. The contents were shaken rigorously for 2 h in a reciprocating
shaker and centrifuged to facilitate phase separation. A suitable aliquot, 5-10 ~ of the
hexane phase, was withdrawn and injected into the gaschromatographic-atomic absorption system. Chau et al. [493] pointed out that, as the authenticity of the compounds to be analysed must be preserved, any of the digestion methods with acids or
alkalis is not suitable, and that extraction seemed to be the method of choice for
removing these compounds from samples. For this extraction, they adopted hexane or
benzene for the quantitative extraction of tetramethyllead and tetraethyllead from
fish homogenates suspended in aqueous EDTA solution. Although ionic forms oflead
such as Pb(H), diethyllead dichloride, and trimethyllead acetate do not extract in the
organic phase, any lead compounds that distribute into this phase as tetraalkyllead
will be determined.
Recovery experiments carried out by Chau et al. [493] showed that benzene,
hexane, and octanol gave the most satisfactory recovery of tetraalkyllead compounds
from fish tissues (78-90 %).
Chau et al. [493] found that tetraalkyllead compounds have high vapour pressures
and are not stable in water. It was observed that water containing 4.2 ~g I-I Me 4 Pb
decreased to 2.8 and 3.9 ~g I-I when stored respectively at room temperature and at
4 °c overnight.
Results obtained in measurements of the accumulation of tetramethyllead in rainbow trout indicated that the tetramethyllead content of dead trout tissue increased
from 0.43 mg kg-I (1 days exposure) to 2.09 mg kg-I (3 days exposure). The trout,
after exposure for different periods of time to water containing 3.5 ~g I-I tetramethyllead, were found to contain tetramethyllead.
Butylation of di-, tri- and tetraalkyl compounds followed by gas chromatography
[159], as described in Sect. 2.5.1 for the determination of alkyllead compounds in
sediments, has also been applied to the analysis of fish samples.
Fish samples were homogenized a minimum of five times in a commercial meat
grinder. About 2 g of the homogenized paste was digested in 5 ml of tetramethyl
ammonium hydroxide solution in a water bath at 60°C for 1-2 h until the tissue had
completely dissolved to a pale yellow solution. After cooling, the solution was neutralized with 50 % hydrochloric acid to pH 6-8. The mixture was extracted with 3 ml of
benzene for 2 h in a mechanical shaker after addition of 2 g of sodium chloride and
3 ml sodium diethyl dithiocarbamate. After centrifugation of the mixture, a measured
amount (1 ml) of the benzene was transferred to a glass-stoppered vial and butylated
with 0.2 ml n-butyl magnesium chloride with occasional mixing for around 10 min.
The mixture was washed with 2 ml of sulphuric acid (1 N) to destroy the excess
Grignard reagent. The organic layer was separated in a capped vial and dried with
anhydrous sodium sulphate. Suitable aliquots (10-20~) were injected into the gas
chromatography-atomic absorption spectrometry system for analysis.
The percentage recoveries of trialkyllead and dialkyllead species at the 1-20 ~g lead
added levels were 72-91 % (trimethyllead), 102-81 % (i. e. 91 ± 10 %) (triethyllead)
Fish
described [494]. The extract was injected directly into the column injection port of the
chromatograph. In this method, the frozen fish tissue was homogenized in a Hobart
grinder and a Polytron homogenizer and 2 g of the fish homogenated with 5 ml of
EDT A reagent, and 5 ml of hexane were immediately placed in a 25 ml test tube with a
Teflon lined screw cap. The contents were shaken rigorously for 2 h in a reciprocating
shaker and centrifuged to facilitate phase separation. A suitable aliquot, 5-10 ~ of the
hexane phase, was withdrawn and injected into the gaschromatographic-atomic absorption system. Chau et al. [493] pointed out that, as the authenticity of the compounds to be analysed must be preserved, any of the digestion methods with acids or
alkalis is not suitable, and that extraction seemed to be the method of choice for
removing these compounds from samples. For this extraction, they adopted hexane or
benzene for the quantitative extraction of tetramethyllead and tetraethyllead from
fish homogenates suspended in aqueous EDTA solution. Although ionic forms oflead
such as Pb(H), diethyllead dichloride, and trimethyllead acetate do not extract in the
organic phase, any lead compounds that distribute into this phase as tetraalkyllead
will be determined.
Recovery experiments carried out by Chau et al. [493] showed that benzene,
hexane, and octanol gave the most satisfactory recovery of tetraalkyllead compounds
from fish tissues (78-90 %).
Chau et al. [493] found that tetraalkyllead compounds have high vapour pressures
and are not stable in water. It was observed that water containing 4.2 ~g I-I Me 4 Pb
decreased to 2.8 and 3.9 ~g I-I when stored respectively at room temperature and at
4 °c overnight.
Results obtained in measurements of the accumulation of tetramethyllead in rainbow trout indicated that the tetramethyllead content of dead trout tissue increased
from 0.43 mg kg-I (1 days exposure) to 2.09 mg kg-I (3 days exposure). The trout,
after exposure for different periods of time to water containing 3.5 ~g I-I tetramethyllead, were found to contain tetramethyllead.
Butylation of di-, tri- and tetraalkyl compounds followed by gas chromatography
[159], as described in Sect. 2.5.1 for the determination of alkyllead compounds in
sediments, has also been applied to the analysis of fish samples.
Fish samples were homogenized a minimum of five times in a commercial meat
grinder. About 2 g of the homogenized paste was digested in 5 ml of tetramethyl
ammonium hydroxide solution in a water bath at 60°C for 1-2 h until the tissue had
completely dissolved to a pale yellow solution. After cooling, the solution was neutralized with 50 % hydrochloric acid to pH 6-8. The mixture was extracted with 3 ml of
benzene for 2 h in a mechanical shaker after addition of 2 g of sodium chloride and
3 ml sodium diethyl dithiocarbamate. After centrifugation of the mixture, a measured
amount (1 ml) of the benzene was transferred to a glass-stoppered vial and butylated
with 0.2 ml n-butyl magnesium chloride with occasional mixing for around 10 min.
The mixture was washed with 2 ml of sulphuric acid (1 N) to destroy the excess
Grignard reagent. The organic layer was separated in a capped vial and dried with
anhydrous sodium sulphate. Suitable aliquots (10-20~) were injected into the gas
chromatography-atomic absorption spectrometry system for analysis.
The percentage recoveries of trialkyllead and dialkyllead species at the 1-20 ~g lead
added levels were 72-91 % (trimethyllead), 102-81 % (i. e. 91 ± 10 %) (triethyllead)