Table 3.

QC samples and acceptance criteria for selenium analysis of fish tissue

QC operation	Frequency	Acceptance Limit	Summary of QC findings
Method blank	1 method blank per batch of up to 20 field samples (Lab opted to run four method blanks per batch)	Less than the sample size-specific MDL determined for this study or less than one-tenth the concentration of an associated sample	None of the method blanks were above the sample size-specific MDLs (43.2 ng/g for nominal 1-g plug samples or 44.9 ng/g for nominal 5-g homogenized fillet samples)
Laboratory control sample (LCS)	1 LCS per batch of up to 20 field samples	80–120% recovery	None of the laboratory control sample results fell outside the acceptance limits. Recoveries ranged from 92 to 108% overall
Reference material sample (lab used DORM-4 from the National Research Council of Canada)	1 per batch of up to 20 field samples	75–125% recovery	None of the reference sample results fell outside the acceptance limits. Recoveries ranged from 90 to 110% overall
Matrix spike sample	1 per every 20 homogenized fillet tissue samples (not required for plug samples)	70–130% recovery	None of the matrix spike sample results associated with the homogenized fillet tissue batches fell outside the acceptance limits. Recoveries ranged from 72 to 106% overall