ABSTRACT
Four spectrophotometric procedures [A-D] for the determination of pantoprazole sodium were investigated. Procedures A and B are stability-indicating methods to determine the intact drug in presence of its degradation products; sulfenamide and sulfenic acid prepared by degrading the pure drug in borate buffer [pH 8] at 37C for 5 days. Procedure A is based on first derivative spectrophotometric measurement in ethanol at 305 nm, whilst procedure B involves coupling of the drug with 2,6-dichloroquinone chlorimide in ethanoldimethylformamide mixture to yield a purple coloured product picked at 515 nm. Procedures C and D depend on charge transfer complexation with dichlorophenol indophenol and dichloronaphthoquinone in CHCl3-methanol and dimethylformamide yielding blue and orange radical anions with lambda max at 640 and 495 nm, respectively. Regression analysis of Beer's plots show good correlations [r=0.9992- 0.9999] and the calibration curves are linear over the ranges of 5-20 mug ml-1, 30-240 mug ml-1, 2-16 mug ml-1 and 40-320 mug ml-1 for procedures A,B,C and D, respectively. The detection limits range between 0.14 and 4.16 mug ml-1. Procedures A and B retain their accuracies in presence of up to 60% and 30% of pantoprazole degradation products, respectively. The average recoveries for commercial tablets are 98.9-100.4%. The results proved to be reproducible and in accordance with those given by a compendial method[11]