quantitatively transferred to 200 ml, tall-form Pyrex beakers using 
redistilled HNO,. The total volume of HNO; was then adjusted to 10 
ml and the beakers covered with watch glasses. The samples were 
heated on a hot plate to near dryness and then removed and allowed 
to cool. Next, 2 ml of 30% H,0, (ULTREX) were added. The samples 
were again placed on a hot plate and heated until the oxidative 
frothing ceased. The samples were cooled and brought to volume in 
50 ml polypropylene flasks with deionized Milli-Q water. The 
samples were then transferred to labeled 60 ml polyethylene bottles 
until subsequent analysis. 
After the initial treatment, a modification of EPA 
standard methods was used for sample preparation for the analysis 
of Hg. Approximately 1 g wet weight of tissues was weighed into 
labeled 50 ml borosilicate bottles with polypropylene screw caps. 
Next, 5 ml of redistilled HNO, were added. The samples were then 
loosely capped and allowed to stand overnight at room temperature 
in the polyethylene hood. To each sample, 5 ml of Hg-free H,SO, 
were added, and the samples were heated in a 95°C water bath for 
two hours. Next, they were allowed to cool followed by 
refrigeration until time for analysis. NRC Lobster Hepatopancreas 
Tissue (Tort-1) and sample reagent blanks were prepared in the same 
manner as the samples. 
Samples were analyzed by atomic absorption 
spectrophotometry (AAS) using both flame (Table 2-3) and graphite 
(Table 2-4) furnaces according to conditions described in Perkin- 
Elmer Instrument manuals. The instrument used was a Perkin-Elmer 
603 equipped with Air/C,H, and N,0/C,H, burners, an HGA-2200 graphite 
furnace, an AS-1 Autosampler, a deuterium (D,) lamp background 
corrector, and a Perkin-Elmer 056 Recorder. The D, background 
corrector was used for all analyses. Standard additions were 
routinely performed along with standard calibrations. When the two 
calibration curves deviated significantly, calculation of sample 
concentrations were based upon the standard addition calibration. 
When agreement was good, a combination of the standard 
addition/standard calibration was used. Sample blanks and NRC 
standards were analyzed in the same manner as the samples. AAS 
working standards were prepared from a mixed 10 ppm stock in 1% 
HNO, uSing Fisher 1000 ppm standards. 
Measurements of the concentrations of Hg were conducted 
by cold vapor atomic absorption spectrophotometry using a 
Laboratory Data Control #1235 Mercury Monitor equipped with a 
Perkin-Elmer 023 recorder. Samples were reduced to destroy the 
excess KMnO, using a 10% solution of NH,OH*HCl in 10% NaCl. Next, 
the samples were reduced to the Hg® state using a 20% solution of 
SnCl, in 3N HCl. The resulting Hg vapor was purged with N, through 
the above described system. Sample blanks and NRC Lobster 
Hepatopancreas Tissue were analyzed in the same manner as the 
samples. Working standards were prepared from a 10 ppm stock in 
ifat 
