Decadic attenuance measurements at 280 nm (D280) of the samples were made using the same cuvette as the blank (formulation buffer prepared as indicated in ESM). Note that the NISTmAb sample was measured directly without further dilution or other preparation steps. The Blank D280 was subtracted from each RM sample D280 to provide a Corrected D280 (Dcorr). Concentration of the NISTmAb was determined utilizing a theoretical extinction coefficient (ε) of 1.42 (mL mg−1 cm−1) . The equation used for calculation of the concentration (C) was1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ C=\frac{D_{corr}}{\varepsilon \bullet b} $$\end{document}C=Dcorrε∙bwith a path length (b) of 0.05092 cm.