184
Crustacea and Molluscs
tion for 20 independent analyses, and was 7, 7,6,14 and 8 %. Recoveries were between
90 and 107 %, (i. e. 98.5 ;;;; 8.5 %).
Amiard et al. [556] applied Zeeman atomic absorption spectrometry to the determination of silver, cadmium, chromium, copper, manganese, nickel, lead, and selenium in oyster and lobster. Aliquots (100 mg powdered sample) were digested in I ml
concentrated nitric acid at 95°C for I h, the volume adjusted to 4 ml with deionized
water, and analysed using a graphite furnace coated with tantalum carbide. Detection
levels were less than Illg kg-I for silver, cadmium, and manganese, about Illg kg-I for
chromium and lead, 5 Ilg kg-I for copper and nickel, and 15 Ilg kg-I for selenium.
Variation coefficients were 5-10 % for 2 series of 6 determinations and experimental
values agreed with certified values.
Inductively Coupled Plasma Atomic Emission Spectrometry. deOliveira et al. [278]
have described a technique based on continuous hydride generation coupled to an
inductively coupled plasma-echelle spectrometer for the determination of arsenic,
antimony, and selenium in oysters in amounts down to Illg I-I. This procedure has
been discussed under multielement analysis, Sect.4.2.15, in connection with the
determination of these three elements in marine sediments.
Ridout et al. [557] used inductively coupled plasma atomic emission spectrometry
to determine various elements in nitric acid digests of lobster hepatopancreas.
Neutron Activation Analysis. Chisela et al. [558] used epithermal and thermal neutron activation analysis to determine arsenic, bromine, cadmium, iron, manganese,
molybdenum, nickel, rubidium, selenium, strontium, and zinc in lobster. Table 8.9
shows values for element contents obtained and the corresponding detection limits,
together with recommended NBS values obtained for SRM 1566 reference oyster
tissue. Typical spectra are shown in Fig. 8.1.
The reliability of the concentrations determined by the two irradiation techniques
can be evaluated in terms of the precision and accuracy achieved, defined as the
difference between the mean and the certified value. For many elements, good precision is achieved with conventional thermal neutron activations (RNAA). This is
simply because many elements have essentially the same response to thermal neutrons, and the activation yields are generally high with little or no discrimination. In
epithermal activation (ENAA), however, selectivity is more pronounced and good
precision is usually obtained fot those elements which exhibit favourable resonance
cross-section characteristics. However, in both instances, the matrix composition of
the sample may influence the precision. The accuracy of determinations, on the other
hand, is comparable for many elements in both activation techniques.
Anodic Scanning Voltammetry. The application of this technique to the determination of trace elements in crustacea has been discussed by Florence [559].
X-ray Fluorescence Spectrometry. Zeisler et al. [560] determined 44 elements in
digest of marine bivalve tissue using this technique. He also used neutron capture,
gamma activation analysis, and neutron activation. analysis.
Photon Activation Analysis. The photon activation analysis technique [280] described under multielement analysis in Sect. 4.2.15 for the analysis of marine sediments
Crustacea and Molluscs
tion for 20 independent analyses, and was 7, 7,6,14 and 8 %. Recoveries were between
90 and 107 %, (i. e. 98.5 ;;;; 8.5 %).
Amiard et al. [556] applied Zeeman atomic absorption spectrometry to the determination of silver, cadmium, chromium, copper, manganese, nickel, lead, and selenium in oyster and lobster. Aliquots (100 mg powdered sample) were digested in I ml
concentrated nitric acid at 95°C for I h, the volume adjusted to 4 ml with deionized
water, and analysed using a graphite furnace coated with tantalum carbide. Detection
levels were less than Illg kg-I for silver, cadmium, and manganese, about Illg kg-I for
chromium and lead, 5 Ilg kg-I for copper and nickel, and 15 Ilg kg-I for selenium.
Variation coefficients were 5-10 % for 2 series of 6 determinations and experimental
values agreed with certified values.
Inductively Coupled Plasma Atomic Emission Spectrometry. deOliveira et al. [278]
have described a technique based on continuous hydride generation coupled to an
inductively coupled plasma-echelle spectrometer for the determination of arsenic,
antimony, and selenium in oysters in amounts down to Illg I-I. This procedure has
been discussed under multielement analysis, Sect.4.2.15, in connection with the
determination of these three elements in marine sediments.
Ridout et al. [557] used inductively coupled plasma atomic emission spectrometry
to determine various elements in nitric acid digests of lobster hepatopancreas.
Neutron Activation Analysis. Chisela et al. [558] used epithermal and thermal neutron activation analysis to determine arsenic, bromine, cadmium, iron, manganese,
molybdenum, nickel, rubidium, selenium, strontium, and zinc in lobster. Table 8.9
shows values for element contents obtained and the corresponding detection limits,
together with recommended NBS values obtained for SRM 1566 reference oyster
tissue. Typical spectra are shown in Fig. 8.1.
The reliability of the concentrations determined by the two irradiation techniques
can be evaluated in terms of the precision and accuracy achieved, defined as the
difference between the mean and the certified value. For many elements, good precision is achieved with conventional thermal neutron activations (RNAA). This is
simply because many elements have essentially the same response to thermal neutrons, and the activation yields are generally high with little or no discrimination. In
epithermal activation (ENAA), however, selectivity is more pronounced and good
precision is usually obtained fot those elements which exhibit favourable resonance
cross-section characteristics. However, in both instances, the matrix composition of
the sample may influence the precision. The accuracy of determinations, on the other
hand, is comparable for many elements in both activation techniques.
Anodic Scanning Voltammetry. The application of this technique to the determination of trace elements in crustacea has been discussed by Florence [559].
X-ray Fluorescence Spectrometry. Zeisler et al. [560] determined 44 elements in
digest of marine bivalve tissue using this technique. He also used neutron capture,
gamma activation analysis, and neutron activation. analysis.
Photon Activation Analysis. The photon activation analysis technique [280] described under multielement analysis in Sect. 4.2.15 for the analysis of marine sediments