CHAPTER 7
Fish
7.1
Metals
7.1.1
Arsenic
The arsine generation-spectrophotometric procedure [247] for the determination of
arsenic, described under arsenic in Sect. 4.2.1 for the determination of arsenic in
marine sediments, has also been applied to the determination of arsenic in fish. The
sample is first digested with a mixture of nitric, sulphuric and perchloric acids. Spiked
samples of crayfish gave a 98-100 % recovery of arsenic by this procedure.
Agemian and Thomson [353] have described a semi-automated atomic absorption spectrometric method for the determination of arsenic in wet homogenized
fish tissue. A combination of nitric, perchloric and sulphuric acids is used to
dissolve high fat fish tissues at 140-180°C in a glass tube. Extracts are then
analysed by reduction to arsine with sodium borohydride, followed by atomic
absorption spectrophotometry with quartz tube atomization. Average recoveries
of arsenic(III), arsenic(V), p-arsalinic acid, benzene arsenic acid, methylarsenic,
and triphenylarsine oxide through this procedure were between 90 and 102 %.
Arsenic found in NBS standard bovine liver (SRM 1577) reference sample was
500 ± 10 mg kg-I against a certified value of 550 ± 5 mg kg-I. Arsenic levels found
in fish samples ranged from 0.26 to 0.44 mg kg-I, determined with a coefficient of
variation of 7-15 %.
Brooke and Evans [354] described two methods for the digestion of fish samples
prior to determination of arsenic down to 0.02 mg kg- I by hydride generation atomic
absorption spectrometry.
The first method involves separation of the inorganic arsenic by distilling it from
6.6 N hydrochloric acid. The second method involved chelation and extraction of
inorganic arsenic after sample dissolution in sodium hydroxide solution, with subsequent back extraction and oxidation. In both methods the arsenic concentration is
measured, after hydride generation by atomic-absorption spectrophotometry with
atomization in a flame-heated silica tube: with the first method the solution contains
arsenic(III), and in the second the solution contains arsenic(V). Results obtained by
both methods are in agreement over a range of samples. The distillation method is
favoured for reasons of efficiency and economy in time.
Fish
7.1
Metals
7.1.1
Arsenic
The arsine generation-spectrophotometric procedure [247] for the determination of
arsenic, described under arsenic in Sect. 4.2.1 for the determination of arsenic in
marine sediments, has also been applied to the determination of arsenic in fish. The
sample is first digested with a mixture of nitric, sulphuric and perchloric acids. Spiked
samples of crayfish gave a 98-100 % recovery of arsenic by this procedure.
Agemian and Thomson [353] have described a semi-automated atomic absorption spectrometric method for the determination of arsenic in wet homogenized
fish tissue. A combination of nitric, perchloric and sulphuric acids is used to
dissolve high fat fish tissues at 140-180°C in a glass tube. Extracts are then
analysed by reduction to arsine with sodium borohydride, followed by atomic
absorption spectrophotometry with quartz tube atomization. Average recoveries
of arsenic(III), arsenic(V), p-arsalinic acid, benzene arsenic acid, methylarsenic,
and triphenylarsine oxide through this procedure were between 90 and 102 %.
Arsenic found in NBS standard bovine liver (SRM 1577) reference sample was
500 ± 10 mg kg-I against a certified value of 550 ± 5 mg kg-I. Arsenic levels found
in fish samples ranged from 0.26 to 0.44 mg kg-I, determined with a coefficient of
variation of 7-15 %.
Brooke and Evans [354] described two methods for the digestion of fish samples
prior to determination of arsenic down to 0.02 mg kg- I by hydride generation atomic
absorption spectrometry.
The first method involves separation of the inorganic arsenic by distilling it from
6.6 N hydrochloric acid. The second method involved chelation and extraction of
inorganic arsenic after sample dissolution in sodium hydroxide solution, with subsequent back extraction and oxidation. In both methods the arsenic concentration is
measured, after hydride generation by atomic-absorption spectrophotometry with
atomization in a flame-heated silica tube: with the first method the solution contains
arsenic(III), and in the second the solution contains arsenic(V). Results obtained by
both methods are in agreement over a range of samples. The distillation method is
favoured for reasons of efficiency and economy in time.