4.2
Metals
4.2.1
Arsenic
Metals
91
Maher [247] has described a procedure for the determination of total arsenic in
marine sediments. The sample is first digested with a mixture of nitric, sulphuric, and
perchloric acids. Then arsenic is converted into arsine using a zinc reductor column,
the evolved arsine is trapped in a potassium iodide-iodine solution, and the arsenic
determined spectrophotometrically at 866 nm as the arseno-molybdenum blue complex. The detection limit is 0.05 mg kg- I dry sediment and the coefficient of variation
5.1 % at this level. The method is free from interferences by other elements at levels
normally found in marine sediments Values of 9.7 ± 0.3 and 13.2 ± 0.4 mg kg- I
obtained for NBS reference waters SRM lS71 and SRM 1566 were in good agreement,
respectively, with the nominal values of 10.2 ± and 13.4 ± mg kg-I.
Siu et al. [248] determined arsenic in marine sediments down to 11lg kg- I by
digestion with concentrated acid and derivatization with 2.3 mercapto-propanol and
electron capture gas chromatography.
Brzezinska-Pandyn et al. [249] compared five methods for the determination of
arsenic in marine and river sediments. The results obtained by graphite furnace
atomic absorption spectrometry, neutron activation analysis, combined furnace flame
atomic absorption ICPAES and flow injection/hydride generation ICPAES showed
that all methods were appropriate for arsenic determinations higher than 5 mg kg- I in
sediments. Graphite furnace atomic absorption spectrometry had a detection limit of
0.5-1 mg kg-I.
4.2.2
Bismuth
Lee [250] has used flameless atomic absorption spectrometry with hydride generation
to determine down to 6 Ilg kg-I of bismuth in marine sediments. Precision is 6.7 % at
the 14 j.lg kg-I bismuth level. The sediment (0.5 g) is completely digested with nitric
acid, perchloric acid, and hydrochloric acid-hydrofluoric acid on a hot plate. The
residue is dissolved in 50 mIl N hydrochloric acid. The bismuth is reduced in solution
by sodium borohydride to bismuthine, stripped with helium, and collected in situ in a
modified carbon rod atomizer. The collected bismuth is subsequently atomized by
increasing the atomizer temperature, and detected by an atomic absorption spectrometer. High concentrations of cobalt, copper, gold, molybdenum, nickel, palladium, platinum, selenium, silver, and tellurium interfere in this procedure. The results obtained in
bismuth determinations on sediments taken in Narragansett Bay ranged from 0.27 to
0.64 mg kg- I and from the North Pacific Ocean from 0.10 to 0.12 mg kg-I.
Metals
4.2.1
Arsenic
Metals
91
Maher [247] has described a procedure for the determination of total arsenic in
marine sediments. The sample is first digested with a mixture of nitric, sulphuric, and
perchloric acids. Then arsenic is converted into arsine using a zinc reductor column,
the evolved arsine is trapped in a potassium iodide-iodine solution, and the arsenic
determined spectrophotometrically at 866 nm as the arseno-molybdenum blue complex. The detection limit is 0.05 mg kg- I dry sediment and the coefficient of variation
5.1 % at this level. The method is free from interferences by other elements at levels
normally found in marine sediments Values of 9.7 ± 0.3 and 13.2 ± 0.4 mg kg- I
obtained for NBS reference waters SRM lS71 and SRM 1566 were in good agreement,
respectively, with the nominal values of 10.2 ± and 13.4 ± mg kg-I.
Siu et al. [248] determined arsenic in marine sediments down to 11lg kg- I by
digestion with concentrated acid and derivatization with 2.3 mercapto-propanol and
electron capture gas chromatography.
Brzezinska-Pandyn et al. [249] compared five methods for the determination of
arsenic in marine and river sediments. The results obtained by graphite furnace
atomic absorption spectrometry, neutron activation analysis, combined furnace flame
atomic absorption ICPAES and flow injection/hydride generation ICPAES showed
that all methods were appropriate for arsenic determinations higher than 5 mg kg- I in
sediments. Graphite furnace atomic absorption spectrometry had a detection limit of
0.5-1 mg kg-I.
4.2.2
Bismuth
Lee [250] has used flameless atomic absorption spectrometry with hydride generation
to determine down to 6 Ilg kg-I of bismuth in marine sediments. Precision is 6.7 % at
the 14 j.lg kg-I bismuth level. The sediment (0.5 g) is completely digested with nitric
acid, perchloric acid, and hydrochloric acid-hydrofluoric acid on a hot plate. The
residue is dissolved in 50 mIl N hydrochloric acid. The bismuth is reduced in solution
by sodium borohydride to bismuthine, stripped with helium, and collected in situ in a
modified carbon rod atomizer. The collected bismuth is subsequently atomized by
increasing the atomizer temperature, and detected by an atomic absorption spectrometer. High concentrations of cobalt, copper, gold, molybdenum, nickel, palladium, platinum, selenium, silver, and tellurium interfere in this procedure. The results obtained in
bismuth determinations on sediments taken in Narragansett Bay ranged from 0.27 to
0.64 mg kg- I and from the North Pacific Ocean from 0.10 to 0.12 mg kg-I.