134
Fish
measurement by the flameless AAS or by utilising a much stronger reducing agent at
the arsine generation stage. It appears that some component{s) of the matrix, which is
destroyed or eliminated during dry ashing but not during wet digestion, depresses the
release of arsenic as arsine and also suppresses the arsenic signal in flame and
flameless atomic absorption spectrometry, unless nickel salts are added to the digest
prior to measurement.
The results of the fifth exercise show that the majority of participants can produce
comparable (i. e. inter-laboratory coefficient of variation of 10 %), and accurate data
for cadmium but not for lead.
In conclusion, over the nine years of the intercomparison exercise, a progressive
improvement has been shown in the determination of copper, zinc, and mercury. Difficulties are still being encountered in producing comparable data for lead and cadmium at
low tissue concentrations in the range 0.05-0.9IJlllol kg-I, but at higher tissue concentrations (2-12 lJlllol kg-I) there has been little difficulty in the production of accurate data for
cadmium, with somewhat greater difficulty in the case of lead.
Ramelow et al. [385] digested fish samples with concentrated nitric acid in a Teflon
lined bomb for 1.5 h at 150°C prior to the determination of mercury by reduction to
elemental mercury with stannous chloride and determination by cold vapour atomic
absorption spectrometry.
Hydride Generation Atomic Absorption Spectrometry. Welz and Melcher [391] decomposed fish tissue with nitric-sulphuric-perchloric acids in a Teflon lined bomb to
decompose arsenic, selenium, and mercury. Nitric acid alone gave low recoveries for
arsenic and selenium but quantitative recovery for mercury. Final determination of
down to 0.3 mg kg-I arsenic, 0.2 mg kg- I selenium, and 0.005 mg kg- I mercury was
carried out by hydride generation and cold vapour atomic absorption spectrometry.
Inductively Coupled Plasma Atomic Emission spectrometry. The ICPAES [278] procedure described in Sect. 4.2.15 for the determination of arsenic, antimony, and
selenium in sediments, has also been applied to the determination of these elements in
fish. Sample digestion was carried out in open vessels at room temperature using
nitric acid, followed by heating with a mixture of nitric, perchloric, and sulphuric
acids on a hot plate. Accurate determinations (mg kg-I) were obtained by this procedure on NBS Reference sample NBS 1566 (oyster tissue) (certified values in parenthesis) for arsenic 11.1 ± 1.1 (13.4 ± 0.9), antimony 0.42 ± 0.3, and selenium 1.7 ± 0.2
(2.1 ± 0.5) and for NBS 1571 (orchard leaves), arsenic 11.9 ± 0.6 (10.2 ± 2.0), and
antimony 2.8 ± 0.02 (0.08 ± 0.01).
Sakai and May [392] used ICPAES, atomic absorption spectrometry, and hydride
generation atomic absorption spectrometry to determine cadmium, arsenic, boron,
chromium, mercury, molybdenum, nickel, lead, and selenium in common carp. The
highest concentrations found were: arsenic 1.5 mg kg-I, boron 20 mg kg-I, cadmium
0.27 mg kg-I, chromium 2.2 mg kg-I, mercury 2.9 mg kg-I, molybdenum 3.6. mg kg-I,
nickel 2.2 mg kg-I, lead 2.3 mg kg-I, and selenium 5.5 mg kg-I.
Differential Pulse Anodic Stripping Voltammetry. Adeljou et al. [393] used this
technique to determine selenium, copper, lead, and cadmium in fish tissues. Detection
limits were in the !lg kg-I range. Samples were first digested with concentrated nitric
acid and 80 % magnesium nitrate solution, and then dry ashed at 500°C. The ash was
Fish
measurement by the flameless AAS or by utilising a much stronger reducing agent at
the arsine generation stage. It appears that some component{s) of the matrix, which is
destroyed or eliminated during dry ashing but not during wet digestion, depresses the
release of arsenic as arsine and also suppresses the arsenic signal in flame and
flameless atomic absorption spectrometry, unless nickel salts are added to the digest
prior to measurement.
The results of the fifth exercise show that the majority of participants can produce
comparable (i. e. inter-laboratory coefficient of variation of 10 %), and accurate data
for cadmium but not for lead.
In conclusion, over the nine years of the intercomparison exercise, a progressive
improvement has been shown in the determination of copper, zinc, and mercury. Difficulties are still being encountered in producing comparable data for lead and cadmium at
low tissue concentrations in the range 0.05-0.9IJlllol kg-I, but at higher tissue concentrations (2-12 lJlllol kg-I) there has been little difficulty in the production of accurate data for
cadmium, with somewhat greater difficulty in the case of lead.
Ramelow et al. [385] digested fish samples with concentrated nitric acid in a Teflon
lined bomb for 1.5 h at 150°C prior to the determination of mercury by reduction to
elemental mercury with stannous chloride and determination by cold vapour atomic
absorption spectrometry.
Hydride Generation Atomic Absorption Spectrometry. Welz and Melcher [391] decomposed fish tissue with nitric-sulphuric-perchloric acids in a Teflon lined bomb to
decompose arsenic, selenium, and mercury. Nitric acid alone gave low recoveries for
arsenic and selenium but quantitative recovery for mercury. Final determination of
down to 0.3 mg kg-I arsenic, 0.2 mg kg- I selenium, and 0.005 mg kg- I mercury was
carried out by hydride generation and cold vapour atomic absorption spectrometry.
Inductively Coupled Plasma Atomic Emission spectrometry. The ICPAES [278] procedure described in Sect. 4.2.15 for the determination of arsenic, antimony, and
selenium in sediments, has also been applied to the determination of these elements in
fish. Sample digestion was carried out in open vessels at room temperature using
nitric acid, followed by heating with a mixture of nitric, perchloric, and sulphuric
acids on a hot plate. Accurate determinations (mg kg-I) were obtained by this procedure on NBS Reference sample NBS 1566 (oyster tissue) (certified values in parenthesis) for arsenic 11.1 ± 1.1 (13.4 ± 0.9), antimony 0.42 ± 0.3, and selenium 1.7 ± 0.2
(2.1 ± 0.5) and for NBS 1571 (orchard leaves), arsenic 11.9 ± 0.6 (10.2 ± 2.0), and
antimony 2.8 ± 0.02 (0.08 ± 0.01).
Sakai and May [392] used ICPAES, atomic absorption spectrometry, and hydride
generation atomic absorption spectrometry to determine cadmium, arsenic, boron,
chromium, mercury, molybdenum, nickel, lead, and selenium in common carp. The
highest concentrations found were: arsenic 1.5 mg kg-I, boron 20 mg kg-I, cadmium
0.27 mg kg-I, chromium 2.2 mg kg-I, mercury 2.9 mg kg-I, molybdenum 3.6. mg kg-I,
nickel 2.2 mg kg-I, lead 2.3 mg kg-I, and selenium 5.5 mg kg-I.
Differential Pulse Anodic Stripping Voltammetry. Adeljou et al. [393] used this
technique to determine selenium, copper, lead, and cadmium in fish tissues. Detection
limits were in the !lg kg-I range. Samples were first digested with concentrated nitric
acid and 80 % magnesium nitrate solution, and then dry ashed at 500°C. The ash was