International Research Journal of Pharmacy and Medical Sciences ISSN (Online): 2581-3277 38 Mohammed Wafaa Nassar, Khalid A. M. Attia, Ragab A. Said, Ahmed El-Olemy, and Mohamed A. Hasan, ―Determination of Lomefloxacin Hydrochloride by Ion-pair Complex Formation with Ammonium Reineckate Using Atomic Absorption Spectrometry,‖ International Research Journal of Pharmacy and Medical Sciences (IRJPMS), Volume 1, Issue 6, pp. 38-43, 2018. Determination of Lomefloxacin Hydrochloride by Ion-pair Complex Formation with Ammonium Reineckate Using Atomic Absorption Spectrometry Mohammed Wafaa Nassar, Khalid A. M. Attia, Ragab A. Said, Ahmed El-Olemy, Mohamed A. Hasan* Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Al-Azhar University, 11751 Nasr City, Cairo, Egypt Abstract—Lomefloxacin hydrochloride is a fluorinated 4-quinolone or fluoroquinolone antibiotic. In this study, a rapid, specific, accurate and precise atomic absorption spectrometric method has been developed and validated for the determination of lomefloxacin hydrochloride in bulk powder and in pharmaceutical preparation depending on its ability to form stable ion pair complex with ammonium reineckate . This formed complex is insoluble in aqueous solution and can easily be separated by filtration. The precipitate could be dissolved in acetone. Then the amount of chromium in the formed complex of lomefloxacin-reineckate ion pair can be measured directly by atomic absorption spectrometer at 357.9 nm. These amounts are corresponding directly to the concentrations of the reacted lomefloxacin hydrochloride. The linear regression analysis data for the calibration curve shows a good relationship in the range of 15 – 100 μg/ml. The developed method was validated according to the International Conference on Harmonization (ICH) guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by the reported method, and no significant difference was found. Keywords— Lomefloxacin hydrochloride; fluoroquinolone; atomic absorption spectrometry; ammonium reineckate and chromium. I. INTRODUCTION omefloxacin hydrochloride is a fluoroquinolone antibacterial which chemically known as (RS)-1- ethyl-6,8-difluoro-1,4-dihydro-7-(3- methylpiperazin-1-yl)-4-oxoquinoline-3-carboxylic acid hydrochloride, figure 1. Lomefloxacin hydrochloride is a white powder which is soluble in water and methanol with 387.81 molecular weigth. 1 Lomefloxacin exhibits antimicrobial effects on DNA gyrase (bacterial topoisomerase II) and bacterial topoisomerase IV. Inhibition of DNA gyrase results in relaxation of supercoiled DNA, promoting DNA strand breakage. Inhibition of topoisomerase IV impacts chromosomal stabilization during cell division, thus interfering with the separation of newly replicated DNA. It has wider spectrum of activity than nalidixic acid and more favorable pharmacokinetics, allowing its use in systemic infections. It has been used in the treatment of infections including bone and joint infections, gastro-enteritis (including travelers' diarrhea and campylobacter enteritis, cholera, salmonella enteritis, and shigellosis), gonorrhea, infections in immuno compromised patients (neutropenia), Q fever, lower respiratory-tract infections , typhoid and paratyphoid fever. 2 It's non official drug, but literature survey reveals that many HPLC methods were reported for determination of lomefloxacin hydrochloride in pharmaceutical preparations and biological fluids. 3-11 Also atomic absorption 11 , spectrophotometric 12-19 , spectrofluorimetric 20-24 and electrochemical 25-30 methods were reported for determination of lomefloxacin hydrochloride alone or in presence of other fluoroquinolone antibiotics. Reviewing the literature on the determination of lomefloxacin hydrochloride revealed the lack of any atomic absorption spectrometric determination of lomefloxacin hydrochloride using ammonium reineckate as precipitating reagent. The aim of this work is to develop and validate simple, accurate and precise atomic absorption spectrometric method for determination of lomefloxacin hydrochloride in bulk powder and in pharmaceutical preparation depending on its ability to form stable ion pair complex with ammonium reineckate. The main goals of analytical atomic spectrometry are to attain the broadest dynamic range, suppress the matrix effect, eliminate spectral interferences, minimize the time and cost required for sample preparation. Fig. 1. Structural formula of lomefloxacin hydrochloride. II. EXPERIMENTAL 2.1. Instruments:  GBC Elemental atomic absorption flame spectrometer, model: GBC 932 AA (Australia), equipped with air- acetylene burner, spray chamber, adjustable nebulizer and computed with GBC AAS software. Chromium was measured at wavelength 357.9 nm, slit width 0.2 nm, relative noise 1 nm, lamp current 10 mA, integration time 4 seconds. L