Charier, Sandrine published the artcilepH sensors: An efficient fluorescent probe for ratiometric pH measurements in aqueous solutions, Safety of 2-Chloroisonicotinic acid, the publication is Angewandte Chemie, International Edition (2004), 43(36), 4785-4788, database is CAplus and MEDLINE.
Just a litmus paper changes from red to blue with an increase in pH, so the fluorescence emission of the oxazole derivative 1 shifts from green to blue. Ratiometric measurements of the fluorescence emissions of the two species, after one- or two-photon excitation, allow 1 to be employed as a pH sensor over the mid-pH range.
Angewandte Chemie, International Edition published new progress about 6313-54-8. 6313-54-8 belongs to chlorides-buliding-blocks, auxiliary class Pyridine,Chloride,Carboxylic acid, name is 2-Chloroisonicotinic acid, and the molecular formula is C6H4ClNO2, Safety of 2-Chloroisonicotinic acid.
Referemce:
https://en.wikipedia.org/wiki/Chloride,
Chlorides – an overview | ScienceDirect Topics