Mercury in Terrestrial Food Webs of the Idrija Mining Area
293
3.3
Determination of Monomethylmercury Compounds (Me-Hg)
3.3.1
Soil Samples
The technique for determination of monomethylmercury compounds in soil
samples is described in detail elsewhere (Horvat et al. 1988, 1993; Liang et al.
1994a,b). It consists of water vapour distillation, followed by aqueous phase
ethylation, precollection on a Carbotrap or Tenax at room temperature and
separation of ethylated species on a GC column (a Chromo sorb W-AW-DMCS
packed column, 40 cm long, i.d. 2 mm, operated isothermally at 110°C).
Separated mercury species were then transformed into elemental Hg by heating
at 900°C and swept into an atomic fluorescence detector (CV AFS, Brooks Rand:
Model-2). Peak heights were used for calculations.
3.3.2
Plant and Animal Samples
A detailed description and a flow-chart of the quantitative method for
determination of monomethylmercury compounds in biota samples by CV
AAS is given elsewhere (May et al. 1987). The method consists of HClleaching,
followed by ion exchange separation (Dowex lX8, 100-200 mesh) of organic and
inorganic Hg, and conversion of organic Hg into inorganic by UV irradiation. An
aliquot of the sample was then transferred to the reduction cell and mercury
quantitatively determined by gold amalgamation CV AAS (LDC Milton Roy
Detector). In principle, this method allows only the quantification of total
organic mercury compounds. However, through the comparison of different
separation and detection techniques, it is known that when analyzing biota
samples the total organic mercury concentrations correspond to the concentration of mono methylmercury only. In addition, the accuracy of the results was
verified by analyzing certified reference materials (CRMs).
3.4
Analytical Quality Control
Quality control of the results for total and monomethylmercury analyses in
samples was performed by analysis of certified reference materials, CRMs.
Relative standard deviations of replicates in all samples analyzed was from 3 to
8% of the mean. All samples were analyzed in duplicate (or triplicate), and three
blank samples were run with each batch of analyses. The CRMs were also
analyzed in duplicate together with each batch of samples, and data quality
control charts were systematically recorded.
293
3.3
Determination of Monomethylmercury Compounds (Me-Hg)
3.3.1
Soil Samples
The technique for determination of monomethylmercury compounds in soil
samples is described in detail elsewhere (Horvat et al. 1988, 1993; Liang et al.
1994a,b). It consists of water vapour distillation, followed by aqueous phase
ethylation, precollection on a Carbotrap or Tenax at room temperature and
separation of ethylated species on a GC column (a Chromo sorb W-AW-DMCS
packed column, 40 cm long, i.d. 2 mm, operated isothermally at 110°C).
Separated mercury species were then transformed into elemental Hg by heating
at 900°C and swept into an atomic fluorescence detector (CV AFS, Brooks Rand:
Model-2). Peak heights were used for calculations.
3.3.2
Plant and Animal Samples
A detailed description and a flow-chart of the quantitative method for
determination of monomethylmercury compounds in biota samples by CV
AAS is given elsewhere (May et al. 1987). The method consists of HClleaching,
followed by ion exchange separation (Dowex lX8, 100-200 mesh) of organic and
inorganic Hg, and conversion of organic Hg into inorganic by UV irradiation. An
aliquot of the sample was then transferred to the reduction cell and mercury
quantitatively determined by gold amalgamation CV AAS (LDC Milton Roy
Detector). In principle, this method allows only the quantification of total
organic mercury compounds. However, through the comparison of different
separation and detection techniques, it is known that when analyzing biota
samples the total organic mercury concentrations correspond to the concentration of mono methylmercury only. In addition, the accuracy of the results was
verified by analyzing certified reference materials (CRMs).
3.4
Analytical Quality Control
Quality control of the results for total and monomethylmercury analyses in
samples was performed by analysis of certified reference materials, CRMs.
Relative standard deviations of replicates in all samples analyzed was from 3 to
8% of the mean. All samples were analyzed in duplicate (or triplicate), and three
blank samples were run with each batch of analyses. The CRMs were also
analyzed in duplicate together with each batch of samples, and data quality
control charts were systematically recorded.