130
Fish
7.7.8
Tin
The flameless atomic absorption spectrometric method [198], described in Sect. 3.1.5,
has also been applied to the determination of tin in fish. Between 0.4 and 6.6 mg tin
was reported in homogenized fish samples.
7.7.9
Vanadium
The combined ion-exchange spectrophotometric procedure [361], described under
cobalt earlier in this chapter has been applied to the determination of vanadium in
cutlass fish. A recovery of 96.3 % vanadium was obtained by this procedure.
Cation exchange chromatography followed by neutron activation analysis has been
used [384] to determine down to 30 J.lg kg- 1 vanadium in fish.
7.7.70
Multielements
Atomic Absorption Spectrometry. Various workers have discussed the application of
this technique to the determination of elements in fish tissue digests [385-390].
Elements determined include cadmium, lead, copper, manganese, zinc, chromium,
and mercury [385], cadmium, zinc, lead, copper, nickel, cobalt, and silver [386],
copper, zinc, cadmium, nickel, and lead [388], lead, cadmium, copper, and zinc [389]
and lead and cadmium [390].
Various digestion systems have been studied for the decomposition of fish samples
prior to analysis, including digestion with nitric acid-perchloric acid [386, 388], nitric
acid-hydrogen peroxide [387, 389], all in open tubes, or, decomposition with nitric
acid in a closed Teflon lined bomb [385].
Nitric Acid-Sulphuric Acid Digestion. Agemian et al. [388] have reported a simple
and rapid digestion method for the simultaneous acid extraction of chromium, copper, zinc, cadmium, nickel, and lead from high-fat fish tissue. Samples are digested
with nitric (5 m116N) and sulphuric (5 ml 36N) acids at 150°C in a modified aluminium hot-block. The method is specially set up for fish sample sizes of up to 5 g, for
low level detection of these elements. After digestion, acid extracts of the sample are
analysed by direct flame atomic-absorption spectrometry for copper, zinc, and chromium. The other three elements, cadmium, nickel, and lead, are concentrated by
chelation with ammonium tetramethylene dithiocarbamate followed by solvent extraction with isobutyl methyl ketone, and determined by flame atomic-absorption
spectrometry.
Detection limits in whole fish tissue are 0.02 mg kg-l (cadmium), 0.05 mg kg- 1
(nickel), 0.1 mg kg- 1 (lead), and 0.2 mg kg- 1 (chromium, copper and zinc). Recoveries
through the whole analytical procedure ranged from 90 to 110 %. Precisions were in
the range 9.1 % to 12.1 (cadmium), 5-15 % (nickel and copper), 4.3-17.0 % (lead),
3.9-6.7 % (zinc) and 7.9-15 % (chromium).
Fish
7.7.8
Tin
The flameless atomic absorption spectrometric method [198], described in Sect. 3.1.5,
has also been applied to the determination of tin in fish. Between 0.4 and 6.6 mg tin
was reported in homogenized fish samples.
7.7.9
Vanadium
The combined ion-exchange spectrophotometric procedure [361], described under
cobalt earlier in this chapter has been applied to the determination of vanadium in
cutlass fish. A recovery of 96.3 % vanadium was obtained by this procedure.
Cation exchange chromatography followed by neutron activation analysis has been
used [384] to determine down to 30 J.lg kg- 1 vanadium in fish.
7.7.70
Multielements
Atomic Absorption Spectrometry. Various workers have discussed the application of
this technique to the determination of elements in fish tissue digests [385-390].
Elements determined include cadmium, lead, copper, manganese, zinc, chromium,
and mercury [385], cadmium, zinc, lead, copper, nickel, cobalt, and silver [386],
copper, zinc, cadmium, nickel, and lead [388], lead, cadmium, copper, and zinc [389]
and lead and cadmium [390].
Various digestion systems have been studied for the decomposition of fish samples
prior to analysis, including digestion with nitric acid-perchloric acid [386, 388], nitric
acid-hydrogen peroxide [387, 389], all in open tubes, or, decomposition with nitric
acid in a closed Teflon lined bomb [385].
Nitric Acid-Sulphuric Acid Digestion. Agemian et al. [388] have reported a simple
and rapid digestion method for the simultaneous acid extraction of chromium, copper, zinc, cadmium, nickel, and lead from high-fat fish tissue. Samples are digested
with nitric (5 m116N) and sulphuric (5 ml 36N) acids at 150°C in a modified aluminium hot-block. The method is specially set up for fish sample sizes of up to 5 g, for
low level detection of these elements. After digestion, acid extracts of the sample are
analysed by direct flame atomic-absorption spectrometry for copper, zinc, and chromium. The other three elements, cadmium, nickel, and lead, are concentrated by
chelation with ammonium tetramethylene dithiocarbamate followed by solvent extraction with isobutyl methyl ketone, and determined by flame atomic-absorption
spectrometry.
Detection limits in whole fish tissue are 0.02 mg kg-l (cadmium), 0.05 mg kg- 1
(nickel), 0.1 mg kg- 1 (lead), and 0.2 mg kg- 1 (chromium, copper and zinc). Recoveries
through the whole analytical procedure ranged from 90 to 110 %. Precisions were in
the range 9.1 % to 12.1 (cadmium), 5-15 % (nickel and copper), 4.3-17.0 % (lead),
3.9-6.7 % (zinc) and 7.9-15 % (chromium).