122
Fish
fraction (84 % of the total arsenic). Arsenic(III), arsenic(V), monomethylarsonic acid,
dimethylarsinic acid and arsenocholine constituted 4 %. The total arsenic concentration was 18.7 mg kg-I. The detection limit was 0.3 ng arsenic.
7.7.2
Cadmium
Blood and Grant [356] determined cadmium in fish tissue using flameless atomic
absorption spectrometry at 228.8 nm using a tantalum ribbon.
Fish samples were digested by one of two techniques: either 1 ml of the acid
mixture (3 parts concentrated nitric acid by volume: 1 part concentrated sulphuric
acid: 1 part concentrated perchloric acid) was placed together with a weighed sample
(1 to 100 mg) in a covered 3.5-ml polypropylene test tube for 2 hat 74°C in a water
bath and, finally, diluted to 25 ml; or 1 ml of concentrated nitric acid was added to the
sample which was heated for 15 mins at 80-90 °c followed by addition of 1 ml of 10 %
hydrogen peroxide and heating for an additional 15 min.
Mean recoveries obtained on the NBS SRM 1577 reference bovine liver sample with
an authenticated cadmium content of 0.27 ± 0.04 mg kg-I were 96.2 % (nitricperchloric-sulphuric acid digestion) and 84.8 % (nitric acid-hydrogen peroxide digestion). In general, higher results were obtained by the sulphuric-nitric acid digestion
procedure. The higher mean levels (13.1-5.6 mg kg-I) of cadmium in wet blue gill
tissue were found in kidney, gut, heart, gill, and liver and the lowest levels (0.141.7 mg kg-I) in muscle, skin and bone.
In a series of papers, Sperling [357-359] studied the application of flameless
graphite furnace atomic absorption spectrometry to the determination of cadmium in
complex matrices resulting from the digestion of fish and other biological materials.
Organic material in the sample is destroyed before atomization by digestion with
ammonium peroxydisulphate, thereby avoiding loss of volatile cadmium which would
occur in ignition methods at temperatures exceeding 420°C [357]. Cadmium was then
extracted from the digest with a saturated solution of ammonium pyrrolidone dithiocarbamate in carbon tetrachloride [358, 359] and the cadmium in the lower layer
determined by flameless graphite furnace atomic absorption spectrometry.
Poldoski [360] used a molybdenum- and lanthanum-treated pyrolytically coated
graphite tube for the graphite furnace atomic absorption spectrometric determination
of cadmium at 228.8 nm in nitric acid perchloric acid digests of fish tissue. Molybdenum and lanthanum help reduce chemical interferences and interference from uncompensated background signals during analyte atomization.
Digestions were carried out on 0.6 g of dry fish using 10 ml concentrated nitric acid
and 2 ml perchloric acid. After digestion was complete, the residue was dissolved in
10 ml 0.2 % w Iv nitric acid and stored in Nalgene bottles.
Cadmium spiking recovery experiments were carried out on fish tissue samples and
on an authenticated reference sample (NBS SRM 1577 bovine liver) under specified
conditions of analysis. The determination cadmium content on NBS SRM reference
fish sample (0.31 ± 0.05 mg kg-I) is in good agreement with the nominal value
(0.27 ± 0.04 mg kg-I). In addition, 0.038 mg kg- I of cadmium was found in whole
catfish and blue gill fish and average analytical recoveries on the fish samples were
Fish
fraction (84 % of the total arsenic). Arsenic(III), arsenic(V), monomethylarsonic acid,
dimethylarsinic acid and arsenocholine constituted 4 %. The total arsenic concentration was 18.7 mg kg-I. The detection limit was 0.3 ng arsenic.
7.7.2
Cadmium
Blood and Grant [356] determined cadmium in fish tissue using flameless atomic
absorption spectrometry at 228.8 nm using a tantalum ribbon.
Fish samples were digested by one of two techniques: either 1 ml of the acid
mixture (3 parts concentrated nitric acid by volume: 1 part concentrated sulphuric
acid: 1 part concentrated perchloric acid) was placed together with a weighed sample
(1 to 100 mg) in a covered 3.5-ml polypropylene test tube for 2 hat 74°C in a water
bath and, finally, diluted to 25 ml; or 1 ml of concentrated nitric acid was added to the
sample which was heated for 15 mins at 80-90 °c followed by addition of 1 ml of 10 %
hydrogen peroxide and heating for an additional 15 min.
Mean recoveries obtained on the NBS SRM 1577 reference bovine liver sample with
an authenticated cadmium content of 0.27 ± 0.04 mg kg-I were 96.2 % (nitricperchloric-sulphuric acid digestion) and 84.8 % (nitric acid-hydrogen peroxide digestion). In general, higher results were obtained by the sulphuric-nitric acid digestion
procedure. The higher mean levels (13.1-5.6 mg kg-I) of cadmium in wet blue gill
tissue were found in kidney, gut, heart, gill, and liver and the lowest levels (0.141.7 mg kg-I) in muscle, skin and bone.
In a series of papers, Sperling [357-359] studied the application of flameless
graphite furnace atomic absorption spectrometry to the determination of cadmium in
complex matrices resulting from the digestion of fish and other biological materials.
Organic material in the sample is destroyed before atomization by digestion with
ammonium peroxydisulphate, thereby avoiding loss of volatile cadmium which would
occur in ignition methods at temperatures exceeding 420°C [357]. Cadmium was then
extracted from the digest with a saturated solution of ammonium pyrrolidone dithiocarbamate in carbon tetrachloride [358, 359] and the cadmium in the lower layer
determined by flameless graphite furnace atomic absorption spectrometry.
Poldoski [360] used a molybdenum- and lanthanum-treated pyrolytically coated
graphite tube for the graphite furnace atomic absorption spectrometric determination
of cadmium at 228.8 nm in nitric acid perchloric acid digests of fish tissue. Molybdenum and lanthanum help reduce chemical interferences and interference from uncompensated background signals during analyte atomization.
Digestions were carried out on 0.6 g of dry fish using 10 ml concentrated nitric acid
and 2 ml perchloric acid. After digestion was complete, the residue was dissolved in
10 ml 0.2 % w Iv nitric acid and stored in Nalgene bottles.
Cadmium spiking recovery experiments were carried out on fish tissue samples and
on an authenticated reference sample (NBS SRM 1577 bovine liver) under specified
conditions of analysis. The determination cadmium content on NBS SRM reference
fish sample (0.31 ± 0.05 mg kg-I) is in good agreement with the nominal value
(0.27 ± 0.04 mg kg-I). In addition, 0.038 mg kg- I of cadmium was found in whole
catfish and blue gill fish and average analytical recoveries on the fish samples were