Physical Chemistry 2012, 2(6): 116-122 DOI: 10.5923/j.pc.20120206.06 A First-Derivative Spectrophotometric Method for the Determination of Ciprofloxacin Hydrochloride in Ophthalmic Solution Edith C. L. Cazedey 1,* , Rudy Bonfilio 2 , Magali B. Araújo 2 , Hérida R. N. Salgado 1 1 Department of Drugs and Medicines, School of Pharmaceutical Sciences, University of São Paulo State, Araraquara, 14801-902, Brazil 2 Department of Drugs and Medicines, School of Pharmaceutical Sciences, Federal University of Alfenas, Alfenas, 37130-000, Brazil Abstract A sensitive, economical and reproducible derivative visible-spectrophotometric method for determination of ciprofloxacin hydrochloride in ophthalmic solution was developed and validated. The method is based on the development of yellow colored product due the reaction between ciprofloxacin hydrochloride and Fe (III). After the reaction, the spectra of the solutions were recorded in the range of 360-500 nm and the first-derivative spectra were obtained by instrumental electronic differentiation using a delta lambda (Δλ) of 8 nm. Analytical responses were units of distance from the central zero base line to the negative peak obtained at 386.4 nm. The method was completely validated according to the ICH guidelines, showing accuracy, precision, selectivity, robustness and linearity. The proposed method is simple, of low cost and provides reliable results in order to be used in quality control of ophthalmic solutions containing ciprofloxacin hydrochloride as active substance. Keywords Ciprofloxacin Hydrochloride, First-Derivative Spectrophotometry, Ophthalmic Solution, Pharmaceutical Analysis, Quinolones 1. Introduction Ciprofloxacin[1 – cyclopropyl – 6 - fluoro - 1,4 – dihydro – 4 – oxo – 7 - (1-piperazinyl) – 3 - quinolone carboxylic acid] (Figure 1) is a second generation fluoroquinolone antimicrobial agent with a wide spectrum of activity against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa[1]. It is believed that the mode of action of fluoroquinolones is through binding DNA-gyrase enzyme[2]. There are several analytical methods described in the literature for the determination of ciprofloxacin hydrochlori de based on high performance liquid chromatography (HPLC) techniques[3-7]. HPLC is described as the official method for analysis of ciprofloxacin in the United States Pharmacopoeia, in the British Pharmacopoeia and in the Brazilian Pharmacopoeia[8-10]. However, HPLC techniques for routine analysis are often time consuming and expensive. For this reason, spectrophotometric techniques continues to be useful alternatives for the assay of different classes of drugs in pharmaceutical formulations and in biological samples due to its simplicity, speed, precision, accuracy, * Corresponding author: crislaignier@yahoo.com.br (Edith C. L. Cazedey) Published online at http://journal.sapub.org/pc Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved reasonable sensibility, and significant economical advantag es over HPLC methods. Numerous methods using visible spectrophotometry [11-41] or UV spectrophotometry[42-44] have been reported for the determination of ciprofloxacin. However, these methods require expensive reagents, involve tedious extraction steps or need time for the reaction between the analyte and the colorimetric reagent. Figure 1. Chemical structure of ciprofloxacin hydrochloride Although there are studies reporting the use of Fe(III) as colorimetric reagent for the spectrophotometric determinati on of ciprofloxacin[16, 21-22], there are no reports on the use of Fe(III) complexes for determination of the studied compound by derivative spectrophotometry. We studied the reaction of hydrochloride ciprofloxacin with