UV-spectrophotometric determination of dissociation constant (pKa) is used routinely in various research fields. This review highlights the structural attributes of organic compounds that exhibit distinct pH-sensitive UV-absorbance for ionized and unionized species qualifying for pKa measurement. Organic compounds must possess a double bond, the chromophore adjacent to the ionizing functional group. Compounds bearing up to five sigma bonds between the chromophore and ionizing group are eligible for UV-spectrophotometric determination of pKa. This review serves as a quick guide for knowledge about structural requirements expediting pKa determination by UV-spectrophotometry. Besides, the study also identified the gap in research on pKa in drug discovery and food chemistry, revealing the necessity of determining pKa at the early stages of drug and food research to enhance the success rate in their development.

A reversed-phased high-performance liquid chromatography–diode-array detection (HPLC–DAD) method has been developed for investigating the stress-dependent degradation of pantoprazole (PTZ) by a photolytic and oxidative mechanism. The developed method separated PTZ from its degradation products on a C18 column with a mobile phase consisted of methanol and water (60:40, v/v; pH 3.0) at a flow rate of 1 mL/min. The linear regression coefficient of 0.9995 was obtained for a concentration range from 5 to 25 μg/mL. The % relative standard deviation for repeatability and intermediate precision were below 0.5% and 1.5%, respectively, while the sensitivity of the method was demonstrated by a limit of detection value of 0.25 μg/mL. The stress sample analyses for PTZ results revealed the formation of a total of 18 degradation products, and out of them, 9 degradation products were common for both photolytic and oxidative degradations. Further, the oxidation by azobisisobutyronitrile produced the highest number of degradation products (11 impurities), 3 of which are more hydrophobic than PTZ. In photolytic degradation, 8 and 7 degradation products were observed with UV radiation and sunlight exposure, respectively. Furthermore, the degradation of pantoprazole sodium injection formulation was carried out under the same stress conditions, and it revealed the formation of 3 common impurities under both stress conditions, but other impurities were not detected in the formulations. Finally, 3 common impurities formed in formulations of PTZ injections, viz., sulfone, N-oxide, and N-oxide sulfone impurities, were identified by spike analyses.