Spectrophotometric Determination of Pantoprazole Sodium in Pharmaceuticals Using N-Bromosuccinimide, Methyl Orange and Indigo Carmine as Reagents

Two sensitive spectrophotometric methods are presented for the assay of pantoprazole sodium sesqui hydrate (PNT) in bulk drug and in formulations using N-bromosuccinimide (NBS) and two dyes, methyl orange and indigo carmine, as reagents. The methods involve the addition of a known excess of NBS to PNT  in acid medium, followed by determination of unreacted oxidant by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B). In both methods, the amount of NBS reacted corresponds to the amount of PNT and  the measured absorbance is found to increase linearly with the concentration of PNT  which is corroborated by the correlation coefficients of 0.9959 and 0.9985 for method A and method B, respectively. The systems obey Beer’s law for 0.1 - 2.0 mg mL-1 and 0.5 - 6.0 mg mL-1 for method A and method B, respectively. The limits of detection and quantification are also reported for both methods. Intra-day and inter-day precision, and accuracy of the methods have been evaluated. The methods were successfully applied to the assay of PNT in tablet preparations and the results were statistically compared with those of the reference method by applying Student’s t-test and F-test. No interference was observed from the common tablet excipients. The accuracy of the methods was further ascertained by performing recovery studies via standard-addition method.