A novel approach based on capillary electrophoresis coupled to augmented multivariate curve resolution-alternating least-squares modeling for the determination of pKa of 2-hydroxy-4,6-dimethylpyrimidine in nicarbazin

• Dissociation constant of 2-hydroxy-4,6-dimethylpyrimidine in nicarbazin was determined.
• No value of pKa is reported in the literature.
• A novel strategy based on second-order data modeling is presented.
• The strategy is different to that employed in previous reports in which first-order data were generated with a FIA system.

The determination of the dissociation constant of 2-hydroxy-4,6-dimethylpyrimidine in nicarbazin was carried out by means of capillary electrophoresis using a dynamic coating of a fused-silica capillary with high-molecular-mass poly(diallyldimethylammonium chloride) (PDDA) implementing two methods: (a) fitting the effective mobility determined from different electrophoretic runs at a single wavelength as a function of pH and (b) a novel modeling strategy of the spectrophotometric second-order data generated with the diode array detector at several wavelengths as a function of pH. The accuracy of the proposed methodologies was verified using robenidine as a model compound with known value of pKa.