Catechol mixtures (2 mL) were prepared, in triplicate, in 15 mL conical tubes to allow immersion of an OHAUS ® ST210 pH electrode. All components, except catechol -including deionized water, Tris buffer, Pi buffer (pH 7.4 and 7.8), Gly, Pro, Lys, and BSA -were mixed and pre-warmed in a 37 °C water bath. 200 L of pre-warmed 156 mM catechol solution was added to the mixture, bringing the final volume to 2 mL and the final catechol concentration to 15.6 mM. The mixture was quickly vortexed and placed back into the water bath to maintain the temperature. A pH meter was immersed into the mixture, and pH was recorded immediately after the addition of catechol.