For quality assurance, the instruments were calibrated based on
a linear four-point calibration curve for each element. Standard
calibration curves with an r2 between 0.999 and 0.998 were run
during measurements. Continuing calibration verification was performed
by analyzing a standard solution and a blank solution for
each of the element at intervals. To verify the quality of the results,
matrix spike/matrix spike duplicates were analyzed with each
batch of about 10 samples for each element. For each run, a triplicate
sample and three blanks were analyzed. An analytical spike
recovery was done by adding increasing amounts of a standard
solution of each element to an aliquot of the digested sample. A
matrix spike recovery of the elements from fish was determined
by adding increasing amounts of the solution of each element to
known amounts of two different samples.