www.scholarsresearchlibrary.com t Available online a Scholars Research Library Der Pharmacia Lettre, 2016, 8 (5):151-157 (http://scholarsresearchlibrary.com/archive.html) ISSN 0975-5071 USA CODEN: DPLEB4 151 Scholar Research Library Absorbance correction method for the simultaneous estimation of norfloxacin and tinidazole in API and combined tablet dosage formulation by UV spectrophotometry Mrunal M. Bulbule and Deepali M. Gangrade* Vivekanand Education Society’s College of Pharmacy, Mumbai University, Chembur (E), Mumbai _____________________________________________________________________________________________ ABSTRACT This research focuses on to the estimation of the concentrations of Norfloxacin and Tinidazole simultaneously in API and combined tablet formulation using a very new , simple, accurate and precised method called ‘Absorption correction method’ using UV spectrophotometer. Beer’s law was obeyed for Norfloxacin in the range of 1-7μg/mL at 278nm and also for Tinidazole in the range of 4-247μg/mL at 316nm. From the accuracy, percentage recovery for Norfloxacin and Tinidazole was found to be in the range of 98.33- 101.68% and 98.52-101.44% respectively. %RSD values reported were less than 2. As all the validation parameters were found to be within the limits given by ICH guideline, the developed method was found to be linear, accurate, precised and rugged. Keywords: Norfloxacin, Tinidazole, Absorption correction method, UV Spectrophotometer _____________________________________________________________________________________________ INTRODUCTION Now a day’s lot of drugs come in the combination form with other drugs. Therefore developing a method for those drugs has become a challenging task for the analyst. This research focuses onto one of the recent UV spectrometric method for estimation of Norfloxacin and Tinidazole in a combined tablet formulation. Method Absorption correction method is a new method for simultaneous detection of drugs. The condition for performing this method is only that one of the drugs must show zero absorbance at the lambda max of the other drug. Drug Information Norfloxacin is a first generation synthetic flouroquinolone which is used as a synthetic chemotherapeutic antibacterial agent [1, 2]. It is used to treat common as well as complicated urinary tract infections [3]. IUPAC name of Norfloxacin is [1-ethyl-6-fluoro-1,4-dihydro-4-oxa-7-(piperazinyl)quinolone-3-carboxylic acid] [4]. Figure I: Structure of norfloxacin