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Abstract
Stability-indicating potentiometric methods have been developed for determination of phenazopyridine hydrochloride (PAP) in the presence of its computationally selected degradation product. Density functional theory has been applied as a computational model to study the energy of PAP metabolites and the results revealed that 2, 3, 6- triaminopridine (TAP) has been the most stable degradation product. Design of PVC and coated graphite sensors has been based on the ion pair of PAP with phosphotungstic acid using dioctylphthalate as a plasticizer. Several significant parameters controlling the performance of the proposed sensors have been examined and optimized. Under the selected optimal conditions the proposed sensors exhibit Nernstian responses in the concentration range of 1.0×10-2 - 1.0×10-5 M with detection limits of 9 x10-6 and 9.6×10-6 M for PVC and coated graphite sensors respectively. Real-time monitoring of the degradation of PAP to TAP has been achieved and the online data obtained showed that PAP degradation followed pseudo-first order kinetics. The proposed sensors have been successfully applied for the determination of PAP in pharmaceutical formulation. Also, the obtained results have been statistically compared to a reported HPLC method indicating no significant difference between the investigated method and the reported one with respect to accuracy and precision.