2.2. Fish samples
Fresh- and salt-water growing fish were used as samples in this
study. Eight different genus of edible frozen fish fillets were purchased
from grocery stores located at Maryville, Missouri. The
average weight of each fish genus group was approximately
0.91 kg. Details of the information of fish specimens, together with
growing environment and collection condition are summarized in
Table 1.
2.3. Homogenization and preservation of fish samples
Homogenization and compositing of fish tissues followed standard
US Environmental Protection Agency (EPA) protocols (U.S.
EPA, 2006). After purchasing, the fish fillets were transported to
the laboratory within an hour and then individually wrapped with
aluminum foil and placed in food-grade polyethylene bags at
80 C. In the laboratory, the muscle tissue of each group of fish
fillets (see Table 1) was homogenized using a Tissuemiser (Fisher
Scientific Power Gen 125) set to rotate at 30000 rpm. After homogenization,
homogenate of each group of fish fillets was combined
uniformly following U.S. EPA protocols (U.S. EPA, 2006) for a representative
sample specimen and then placed in heavy-duty aluminum
foil with appropriate sample identification mark. Following,
all tissue specimens were stored at 80 C prior to extraction.