Metals
183
(iii) Combustion in a stream of oxygen which could be applied for all three elements,
and gave results that were in good agreement with the mean values of an intercalibration.
Pressure decomposition with nitric acid is recommended for mercury, followed by a
sulphuric and perchloric acid treatment for the subsequent determination of arsenic
and selenium (Table 8.7). Detection limits under routine conditions are 0.3 mg kg- 1 for
arsenic, 0.2 mg kg- 1 for selenium, and 0.005 mg kg-l for mercury.
Table 8.8 gives the maximum tolerance levels for several elements that allow an
interference free determination of arsenic, selenium, and mercury.
Solchaga and De La Guardia [555] have proposed a method for acid pressure
extraction, using nitric acid, of cadmium, copper, iron, lead, and zinc in stoppered
borosilicate glass~ followed by flame atomic absorption spectroscopy. The five metals
were determined in a 300-mg single sample of mussel meat. Detection limits were
0.3 mg kg- 1 for cadmium, 0.7 mg kg- 1 for copper, 33.0 mg kg- 1 for iron, 0.7 mg kg- 1 for
lead, and 6.0 mg kg- 1 for zinc. Precision was estimated from the coefficient of variaTable 8.7
Determination of arsenic, selenium, and mercury in marine biological tissue samples
using different composition procedures (from [554])
mg kg-I
Samples Accepted mean
Nitric acid under
Perchloric acid
Oxygen combustion
presure
at 310 gradC
(n = 3)
(n = 4)
(n = 6)
Arsenic
Lobster
25
± 5
15.1 ± 0.4
25.5 ± 0.5
24.6 ± 0.7
Scallops
7.1 ± 2.1
3.5 ± 0.4
7.7 ± 0.2
7.0 ± 0.3
Selenium
Lobster
6.4 ± 0.4
6.4 ± 0.2
6.7 ± 0.2
6.2 ± 0.4
Scallops
0.78 ± 0.08
0.71 ± 0.04
0.87 ± 0.01
0.71 ± 0.08
Mercury
Lobster a
0.30 ± 0.00
0.17 ± 0.04
0.31 ± 0.02
Scallopsb
0.09 ± 0.01
0.07 ± 0.02
0.10 ± 0.01
a Accepted mean 0.256 ± 0.049
b Accepted mean 0.081 ± 0.012
Table 8.8
Maximum tolerable element concentrations in the solution for measurements for an
interference-free determination of arsenic and selenium in 10 ml of 0.5 mol I-I hydrochloric acid
(from [554])
Element or sample to be
Max interferent conen, Jlg 10 ml- I
determined or analyzed
Cu
Fe
Ni
As
Se
As
1000
1000
2
0.01
Se
0.5
5000
2.5
[20)a
[25)a
1 mg of lobster
0.01
0.2
0.02
0.025
0.006
2 mg of scallops
0.01
<
0.2
< 0.02
0.Dl5
0.002
a Values in brackets are for 10 ml of 5.0 mol I-I hydrochloric acid medium. Also shown are the
approximate element concentrations in the sample solution aliquots analyzed
183
(iii) Combustion in a stream of oxygen which could be applied for all three elements,
and gave results that were in good agreement with the mean values of an intercalibration.
Pressure decomposition with nitric acid is recommended for mercury, followed by a
sulphuric and perchloric acid treatment for the subsequent determination of arsenic
and selenium (Table 8.7). Detection limits under routine conditions are 0.3 mg kg- 1 for
arsenic, 0.2 mg kg- 1 for selenium, and 0.005 mg kg-l for mercury.
Table 8.8 gives the maximum tolerance levels for several elements that allow an
interference free determination of arsenic, selenium, and mercury.
Solchaga and De La Guardia [555] have proposed a method for acid pressure
extraction, using nitric acid, of cadmium, copper, iron, lead, and zinc in stoppered
borosilicate glass~ followed by flame atomic absorption spectroscopy. The five metals
were determined in a 300-mg single sample of mussel meat. Detection limits were
0.3 mg kg- 1 for cadmium, 0.7 mg kg- 1 for copper, 33.0 mg kg- 1 for iron, 0.7 mg kg- 1 for
lead, and 6.0 mg kg- 1 for zinc. Precision was estimated from the coefficient of variaTable 8.7
Determination of arsenic, selenium, and mercury in marine biological tissue samples
using different composition procedures (from [554])
mg kg-I
Samples Accepted mean
Nitric acid under
Perchloric acid
Oxygen combustion
presure
at 310 gradC
(n = 3)
(n = 4)
(n = 6)
Arsenic
Lobster
25
± 5
15.1 ± 0.4
25.5 ± 0.5
24.6 ± 0.7
Scallops
7.1 ± 2.1
3.5 ± 0.4
7.7 ± 0.2
7.0 ± 0.3
Selenium
Lobster
6.4 ± 0.4
6.4 ± 0.2
6.7 ± 0.2
6.2 ± 0.4
Scallops
0.78 ± 0.08
0.71 ± 0.04
0.87 ± 0.01
0.71 ± 0.08
Mercury
Lobster a
0.30 ± 0.00
0.17 ± 0.04
0.31 ± 0.02
Scallopsb
0.09 ± 0.01
0.07 ± 0.02
0.10 ± 0.01
a Accepted mean 0.256 ± 0.049
b Accepted mean 0.081 ± 0.012
Table 8.8
Maximum tolerable element concentrations in the solution for measurements for an
interference-free determination of arsenic and selenium in 10 ml of 0.5 mol I-I hydrochloric acid
(from [554])
Element or sample to be
Max interferent conen, Jlg 10 ml- I
determined or analyzed
Cu
Fe
Ni
As
Se
As
1000
1000
2
0.01
Se
0.5
5000
2.5
[20)a
[25)a
1 mg of lobster
0.01
0.2
0.02
0.025
0.006
2 mg of scallops
0.01
<
0.2
< 0.02
0.Dl5
0.002
a Values in brackets are for 10 ml of 5.0 mol I-I hydrochloric acid medium. Also shown are the
approximate element concentrations in the sample solution aliquots analyzed