Universal Buffer : a powerful tool to investigate the impact of pH on photophysical and (photo)chemical properties from 1.9 to 12.

pH can impact a wide range of (photo)chemical (kinetics, thermodynamics or quantum yield…) or photophysicals properties (absorption, emission…). We proposed to present an easy, fast and reproducible new method to tune with a very high precision pH value from 1.5 to 13 based on a so-called Universal Buffer. The latter is made of acetic acid, phosphoric acid and boric acid at 0.04 mol.L-1. To ensure the efficiency and reliability of our procedure, we used it determine the pKa value(s) for a series of indicators from sulfonephtalein derivatives [1] to azonaphtalen derivatives [2]. For BTB (BromoThymol Blue) impressive results were obtained (R² = 0,9999) and a pKa of 7.13 ± 0.01 was found in perfect agreement with literature (7.1). In addition, our procedure was applied to fluorescent compounds such as Quinine, Eosin Y, Rhodamine B and Riboflavine. For Quinine, absorption and emission properties (fluorescence quantum yield, absorption and emission spectrum) of the three acido-alkali forms (QH22+, QH+ and Q) were obtained (Figure 1) as well as pKa and pKa* and compare to the literature 3. Potential applications in research can be also mentioned. (1) BI, Ran; BRION, Aurélien; PERRIN, Rémi; DORÉ, Clément; CLAVIER, Gilles; Piard, J.; L.Shi. Utilisation d’un Tampon Universel pour l’étude d’indicateurs colorés Acido-Basiques (Par Spectrophotométrie UV-Visible). Bulletin de l’Union des Physiciens 2019, 1014, 559–601. (2) BI, Ran; BRION, Aurélien; PERRIN, Rémi; DORÉ, Clément; Piard, J.; L.Shi. Utilisation d’un Tampon Universel Pour l’étude d’indicateurs Colorés Acido-Basiques (Par Spectrophotométrie UV-Visible). Bulletin de l’Union des Physiciens 2019, 1015, 661-. (3) Article Accepted. Bulletin de l’Union des Physiciens.