$S_{\large{\textrm{total}}}=k_{\large{\textrm A}}n_{\large{\textrm A}}+S_{\large{\textrm{reag}}}\hspace{5mm}\textrm{or}\hspace{5mm}S_{\large{\textrm{total}}}=k_{\large{\textrm A}}C_{\large{\textrm A}}+S_{\large{\textrm{reag}}}$
where $$S_{total}$$ is the signal, $$n_A$$ is the moles of analyte, $$C_A$$ is the analyte’s concentration, $$k_A$$ is the method’s sensitivity for the analyte, and $$S_{reag}$$ is the contribution to $$S_{total}$$ from sources other than the sample. To standardize a method we must determine values for $$k_A$$ and $$S_{reag}$$. Strategies for accomplishing this are the subject of this chapter.