Spiking and homogenization of biological matrices for production of reference materials using cryogenic processes.

Biological reference materials (RMs) are essential for quality assurance, traceability of measurement results and for method validation. When addressing new measurement questions or emerging regulatory issues, rigorous large-scale CRM production may not be time efficient or economically practical using current production methods. By amending a relatively small matrix batch with a compound(s) of interest at the homogenization step, the National Institute of Standards and Technology (NIST) can create a custom material on an "as-needed" basis and circumvent the time delay inherent in large-batch production, thereby generating a fit-for-purpose, rapid-response RM. Here, Coho salmon (Oncorhynchus kisutch) was cryohomogenized and spiked with an aquaculture antibiotic and antibiotic metabolite. The resultant material was analyzed using liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS) to determine the effectiveness of the amendment technique in a fresh-frozen matrix by assessing homogeneity and accuracy to the target concentration (e.g. mass fraction). Target mass fractions were achieved for both spike components, with RSDs below 5% in replicate measurements of each compound (n = 8). The stability of the spiked compounds was assessed one year post-production and mass fractions were stable, within 1-6% of the initial measurement results, indicating minimal change to the amended analyte concentrations over time. The results support this method as a promising new technique for custom, small-batch RM generation.