No Quantitation without Representation

At Analytical Perspectives, we have a simple rule. The more standards we use to control various aspects of our procedures, the more QA we impart to the data (i.e., the more confident of the data we and the data end-user become). Over the past several decades, the creation of newly labeled polychlorinated dibenzo-p-dioxin and dibenzofuran (D/F) compounds has allowed us to obtain enhanced quality control, illuminating problems present in analytical procedures. For example, the use of additional labeled D/F and polychlorinated biphenyl congener (PCB) compounds, that are not required in current methods, has allowed us to continuously improve our processes (e.g., the monitoring of selective losses for D/F congeners that occur during fractionation which results in a congener profile distortion that would otherwise be left undocumented), or to achieve a higher degree of reliability and accuracy in the measurement of a TEQ. The inclusion of additional labeled compounds that help us evaluate the sampling process, the solvent rinse concentration process, the extraction process, the fractionation process, and the transfer step process allows a better determination regarding how various congener groups are specifically impacted during analytical procedures. The integration of additional labeled standards can be accomplished with minimal added cost.

Currently, Analytical Perspectives has more labeled D/F standards than is required for any  D/F assay, Method 8290A, Method 23, or Method 1613B labeled standards. Among the newly labeled compounds utilized in our procedures, several are used to monitor Method 23’s solvent rinses in the field (FS; field concentration standards) and their subsequent transfer inside the extraction vessel by the laboratory (TS; transfer standard). The FS and TS help monitor losses during the concentration step of the solvent rinses from stack samples, either during the analytical laboratory testing itself or at the stack tester’s laboratory during the sample recovery. 

For example, during the recent ICR or routinely for worldwide origin samples, solvent jars containing keepers were fortified with known quantities of FS for the purpose of solvent concentration in the field. The TS was then used to make sure that the transfer of concentrated residue (i.e., mostly the ~1 mL of water/solvent and the keepers) to the extraction vessel was complete. Benefits using the FS/TS approach included reduced shipping costs, reduced risks and liabilities associated with the shipment of dangerous goods, and reduced time needed to prepare, or to even receive, the samples for analysis. Based on our early experience, solvents are typically concentrated under conditions conducive to low recoveries, a problem that would have be left unnoticed, had the standards not been present. Through the use of these additional standards, we obtain valuable information on how best to conduct this concentration step in a manner that is truly performance based.

In essence, both the testing laboratory and/or the stack sampler become conscious of the presence of these “microscopic spies” keeping an eye on our actions, and ultimately, our performance.