Evaluation of Performance Characteristics of Multistep Analytical Methods from Collaborative Study of Linked Samples

Following unexpectedly variable results from an international comparison study of the determination of selected polychlorinated biphenyl (PCB) congeners in shellfish tissue, a group of national metrology institutes collaboratively explored the analytical characteristics of their measurement systems using a designed study with four sample materials. This “Uncertainty Suite” consisted of a 10-congener mixture of PCBs in relatively nonvolatile isooctane, a 5-congener mixture in relatively volatile methylene chloride, a methylene chloride extract of freeze-dried mussel (Mytilus edulis) tissue, and the (homogenized) mussel tissue itself. These related-but-different samples presented the participants’ measurement processes with a linked series of analytical challenges. Data evaluation tools were developed to combine and visualize measurement results for the different congeners of interest for each material and, exploiting the linkages among the samples, to help identify causes for observed changes in performanc...