I am following the desorption of a compound from a polymer. Let's imagine that it occurs at a certain rate and most of the compound is desorbed after 5 days (as in the figure). Then, I could use many analytical techniques to follow the compound desorption by measuring at, e.g., t = 1 day and t = 4 d. The concentration difference between these two points is large enough to be detected.
However, if I the desorption is much slower (as in the figure below) and I can only take samples for 10 days, the only way to characterise the desorption rate would be with a much more sensitive analytical technique, as I would need to detect changes from, e.g. 0.98 to 0.96
My question is, supposing that I have a good guess of the concentration differences that I will encounter, how can I choose an analytical technique beforehand based on reported limits of detection and/or quantification? How can I relate limits of quantification with the ability to differentiate a sample at 0.98 and another one at 0.96?