Since the dissociation of ACN is very low (ACN pK a =40 ), all the protons derive f rom the acid, thus the proton concentration in this system can be considered the same than the conjugated base, then: and thus, we used the slope of [H + ] 2 vs. It is noted that the pK a f rom the f our acids had similar values in a range f rom 9 to 10 regardless some of them are considered weak acids. This similar behavior can already be noted f rom the allure of the f luorescence titration curves as the f luorescence vs. acid concentration had a similar behavior in all cases. The strong acidity observed by all the compounds is explained by the inf luence of the electrolyte Bu 4 PF 6 , that creates super-acids due to the ability of PF 6 to associate the protons dissociated f rom the acids already reported in literature . As a result of our calibration of the acidity response of FAM with the Faradaic currents, we were able to f ind the activity of the acids in the complex media that included Bu 4 PF 6 .