Analytical Methods for Measuring Mercury in Water, Sediment, and Biota - Mercury in the Environment - page 30

table 3.2
Selected Methods for the Analysis of Mercury

Analyte Matrix Detector Reference or EPA method Typical MDL

Total Hg Water CVAAS EPA Method 245.1 5-10 ng/L

Total Hg Water CVAFS EPA Method 245.7 0.5-5 ng/L

Total Hg Water CVAFS EPA Method 1631 0.1-0.3 ng/L

Total Hg Water ICP-MS EPA Method 200.8 10 ng/L

Total Hg Water ICP-AES EPA Method 200.7 200 ng/L

Elemental Hg Water CVAFS EPA Method 1631 mod a 0.1-0.3 ng/L

Reactive Hg Water CVAFS EPA Method 1631 mod b 0.1-0.3 ng/L

MMHg Water CVAFS EPA Method 1630 (draft) 0.01-0.05 ng/L

Total Hg Sediment CVAAS EPA Method 245.5 5-10 ng/g

Total Hg Sediment CVAAS EPA Method 7471 10-50 ng/g

Total Hg Sediment DTDAAS EPA Method 7473 5-10 ng/g

Total Hg Sediment CVAFS EPA Method 1631 appendix 0.5-1 ng/g

MMHg Sediment CVAFS EPA Method 1630 mod c 0.01-0.05 ng/g

MMHg Sediment GC-ICP-MS Bjorn et al. (2007) c 0.01-0.05 ng/g

Total Hg Tissue CV AAS EPA Method 245.6 5-10 ng/g

Total Hg Tissue DTDAAS EPA Method 7473 5-10 ng/g

Total Hg Tissue CVAFS EPA Method 1631 appendix 0.5-1 ng/g

Total Hg Blood ICP-MS Palmer et al. (2006) 0.17 g/L

Total Hg Blood FI-AAS Palmer et al. (2006) 0.6 g/L

MMHg Tissue CVAFS EPA Method 1630 mod d 0.5-2 ng/g

AAS atomic absorption spectrometry; CVAAS cold-vapor atomic absorption spectrometry;

CVAFS cold-vapor atomic fl uorescence spectrometry; FI Flow Injection; GC gas chromatography;

ICP-AES inductively coupled plasma atomic emission spectrometry; ICP-MS inductively coupled

plasma mass spectrometry; MDL Method Detection Limit; DTD Direct Thermal Decomposition.

a. Without oxidation or reduction.
b. Without oxidation.
c. Using extraction or distillation to isolate MMHg.
d. Using KOH/methanol digestion to release MMHg (Bloom 1989)

Another factor that must be weighted in choosing a
suitable analytical method is the recognition that mer-
cury can exist in a wide variety of chemical forms that
may or may not be liberated for analysis by the procedures
adopted. Illustrated in Figure 3.2 are the various fractions
or pools of inorganic Hg(II) that can exist in natural water
systems. The common aqueous species of inorganic Hg(II)
in oxygenated freshwater are Hg(OH) 2 0 , and HgCl 2 0 . In
seawater, the dominant inorganic forms are the chlo-
ride species (HgCl 4 2 , HgCl 3 1 , etc). In suboxic to anoxic
waters, polysulfi de species can dominant (e.g., HgS 0 ) if
sulfi de concentration levels exceed Hg concentration lev-
els. Hg(II) also strongly interacts with colloids and sus-
pended particles in aqueous systems to form colloidal or

particulate-bound Hg forms. Mercury also forms numer-
ous stable complexes with well-defi ned organic ligands
(e.g., ethylenediaminetetraacetic acid [EDTA]) and with
dissolved organic matter (DOM) to form organic mercury
compounds. Biologic transformations can convert Hg(II)
to gaseous elemental Hg and methylated Hg forms (see
Figure 3.1). In tissues, mercury can be present in both
inorganic and organo-Hg forms, with higher trophic level
species usually containing predominantly MMHg. In sed-
iments, mercury tends to adsorb preferentially to carbon-
based particles.
To perform a meaningful total Hg analysis, it is essen-
tial to perform a suitable preparation step to release the Hg
from whatever matrix or complexes in which it may reside.