Aqueous LC-MS/MS quantification of α-/β-nicotinamide mononucleotide in dietary supplements using a pentabromophenyl...

In this study, we developed an LC-MS/MS method that enables baseline separation and quantification of α- and β-nicotinamide mononucleotide (NMN) isomers under fully aqueous reversed-phase conditions. At first, three commonly used reversed-phase columns (Polar C18, F5, and PBr) were evaluated, and only the PBr phase provided sufficient stereoselectivity through enhanced π-π stacking, dipole-dipole interactions, and halogen bonding. Using 0.1 % formic acid in water as the mobile phase, the two isomers were baseline resolved within 3 min. The method was validated for linearity, sensitivity, precision, accuracy, and matrix effects. When applied to eight commercial NMN supplements, the analysis revealed substantial variation in isomer composition, including undeclared or inaccurately labeled ingredients. Overall, this work presents the first LC-MS/MS approach capable of isomer-specific NMN analysis under fully aqueous reversed-phase conditions, offering a robust and environmentally compatible platform for product authentication, quality control, and potential applications in pharmacokinetics and metabolomics.