Research Article Manipulating Ratio Spectra for the Spectrophotometric Analysis of Diclofenac Sodium and Pantoprazole Sodium in Laboratory Mixtures and Tablet Formulation Nejal M. Bhatt, 1 Vijay D. Chavada, 1 Mallika Sanyal, 2 and Pranav S. Shrivastav 1 1 Department of Chemistry, School of Sciences, Gujarat University, Ahmedabad, Gujarat 380009, Gujarat, India 2 Department of Chemistry, St. Xavier’s College, Navrangpura, Ahmedabad, Gujarat 380009, Gujarat, India Correspondence should be addressed to Pranav S. Shrivastav; pranav shrivastav@yahoo.com Received 30 August 2013; Accepted 6 January 2014; Published 18 February 2014 Academic Editors: Y. Lu, S. Sultan, and R. Zakrzewski Copyright © 2014 Nejal M. Bhatt et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objective. Tree sensitive, selective, and precise spectrophotometric methods based on manipulation of ratio spectra, have been developed and validated for the determination of diclofenac sodium and pantoprazole sodium. Materials and Methods. Te frst method is based on ratio spectra peak to peak measurement using the amplitudes at 251 and 318 nm; the second method involves the frst derivative of the ratio spectra (Δ = 4 nm) using the peak amplitudes at 326.0 nm for diclofenac sodium and 337.0 nm for pantoprazole sodium. Te third is the method of mean centering of ratio spectra using the values at 318.0nm for both the analytes. Results. All the three methods were linear over the concentration range of 2.0–24.0 g/mL for diclofenac sodium and 2.0–20.0 g/mL for pantoprazole sodium. Te methods were validated according to the ICH guidelines and accuracy, precision, repeatability, and robustness are found to be within the acceptable limit. Te results of single factor ANOVA analysis indicated that there is no signifcant diference among the developed methods. Conclusions. Te developed methods provided simple resolution of this binary combination from laboratory mixtures and pharmaceutical preparations and can be conveniently adopted for routine quality control analysis. 1. Introduction Nonsteroidal anti-infammatory drugs (NSAIDs) are a class of drugs that provide analgesic, antipyretic, and anti- infammatory efects [1]. Diclofenac (DCL, Figure 1(a)) is one of the most prescribed NSAIDs worldwide, used to reduce infammation and as an analgesic to reduce pain in certain other conditions [2]. Te primary mechanism responsible for anti-infammatory, antipyretic, and analgesic action of DCL is thought to be inhibition of prostaglandin synthesis by inhibition of cyclooxygenase (COX) [3]. Inhibition of COX also decreases prostaglandins in the epithelium of the stomach, making it more sensitive to corrosion by gastric acid. Te threats of peptic ulcer on long-term use of DCL require concomitant treatment with proton pump inhibitors as they have been shown to be efective in preventing the development of gastric and duodenal ulcers in high-risk patients taking NSAIDs [4]. Pantoprazole (PAN, Figure 1(b)) is a type of medicine called a proton pump inhibitor (PPI). PAN suppresses the fnal step in gastric acid production by covalently binding to the (H+, K+)-ATPase enzyme system at the secretory surface of the gastric parietal cell. Tis efect leads to inhibition of both basal and stimulated gastric acid secretion, irrespective of the stimulus. Besides inhibiting acid secretion, PAN afords protection against NSAID-induced gastric damage [5], has low potential for drug-drug inter- actions, and is particularly suitable for administration to elderly patients who ofen require concomitant treatment with NSAIDs as no dose adjustment is required during concomitant treatment with both drugs [4]. Literature survey revealed several analytical methods reported for DCL estimation using HPLC [6–10] and elec- troanalytical techniques [11–14]. Aurora-Prado et al. [15] have developed a capillary electrophoresis method for determi- nation of DCL in tablets and compared its performance with that of an HPLC method. Several spectrophotometric Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 495739, 10 pages http://dx.doi.org/10.1155/2014/495739