Fluorimetric Determination of Gatifloxacin in Aqueous

Analytical Letters

ISSN: 0003-2719 (Print) 1532-236X (Online) Journal homepage: http://www.tandfonline.com/loi/lanl20

Fluorimetric Determination of Gatifloxacin in Aqueous, Pure and Pharmaceutical Formulations Taha M. A. Razek , Ramzia I. El‐Baqary & Ahmed E. Ramadan To cite this article: Taha M. A. Razek , Ramzia I. El‐Baqary & Ahmed E. Ramadan (2008) Fluorimetric Determination of Gatifloxacin in Aqueous, Pure and Pharmaceutical Formulations, Analytical Letters, 41:3, 417-423, DOI: 10.1080/00032710701746816 To link to this article: http://dx.doi.org/10.1080/00032710701746816

Published online: 11 Feb 2008.

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Date: 16 May 2017, At: 04:10

Analytical Letters, 41: 417–423, 2008 Copyright # Taylor & Francis Group, LLC ISSN 0003-2719 print/1532-236X online DOI: 10.1080/00032710701746816

PHARMACEUTICAL ANALYSIS

Fluorimetric Determination of Gatifloxacin in Aqueous, Pure and Pharmaceutical Formulations Taha M. A. Razek,1 Ramzia I. El-Baqary,2 and Ahmed E. Ramadan1 1

Environmental Basic Science Dept., Institute of Environmental Studies and Research, Ain Shams University, Abbassia, Cairo, Egypt 2 Faculty of Pharmacy, Chemistry Dept., Cairo University, Cairo, Egypt

Abstract: A spectrofluorimetric method was developed for the determination of gatifloxacin. The emission peak for gatifloxacin was recorded at 495 nm upon excitation at 291 nm. The fluorescence process was pH dependent. The dynamic range for the method was 16 –80 ng ml21with detection limit of 3.97 ng ml21. A linear relationship between the fluorescence intensity and the concentration of gatifloxacin solution was obtained with r2 of 0.9968. The method has successfully applied to the determination of gatifloxacin in pure, authentic and aqueous samples. Keywords: Gatifloxacin determination, fluorimetry, pharmaceutical formulations

INTRODUCTION Gatifloxacin (1-cyclopropyl-6-fluro-1,4-dihydro-8-methoxy-7-(3-methyl-1piperazinyl)-4-oxo-3 quinolinecarboxylic acid) is a synthetic broad spectrum fluoroquinolone antibiotic structurally related to nalidixic acid (Sweetman 2002) (Fig. 1). It has a wide range of activity against gram positive and gram negative bacteria. Fluoroquinolones are used for the treatment of upper and lower Received 3 October 2007; accepted 1 November 2007 Address correspondence to Taha M. A. Razek, Environmental Basic Science Dept., Institute of Environmental Studies and Research, Ain Shams University, Abbassia, Cairo, Egypt. E-mail: [email protected] 417

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T. M. A. Razek et al.

Figure 1.

Gatifloxacin structure.

respiratory infections, gonorrhea, gastroenteritis, and urinary tract infections (Hairui et al. 2002). Few analytical methods have been reported for the determination of gatifloxacin in pure, pharmaceutical dosage forms and in biological fluids. Among these methods HPLC has been proposed for determining the drug in human serum (Overholser et al. 2003; Santoro et al. 2006) and pharmaceutical products (Zhu et al. 2002; Nguyen et al. 2004). Methods based on fluorimetry (Ocana et al. 2005; Venugopal and Saha 2005) and microbiology has been developed (Piddock and Johnson 2002). In this study a direct flourimetric method has been developed for the determination of gatifloxacin in pure and pharmaceutical dosage forms. The sensitivity and reproducibility of the method is sufficiently high to allow an accurate determination of low concentrations of gatifloxacin.

EXPERIMENTAL Reagent and Materials All chemicals were of analytical reagent grade, unless stated otherwise. Doubly distilled water was used throughout; phosphoric acid and potassium chloride were obtained from Adwic, Egypt. Gatifloxacin was obtained from Bristol-Myers Squibb (Wallingford, CT) & Tequin tablets (400 mg/ Tab.) were purchased from local market. Potassium chloride buffer (pH 2.2) was

Figure 2.

Ex/Em spectra for gatifloxacin.

Fluorimetric Determination of Gatifloxacin

Figure 3.

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The effect of pH on the fluorescence intensity of gatifloxacin.

prepared by mixing 50 ml of equimolar 0.2 mol l21 aqueous potassium chloride solution with 7.8 ml hydrochloric acid solution and then the solution was completed with water to 200 ml. A solution of 2.5 mmole l21 potassium phosphate buffer was prepared by transferring 170 + 1 mg of potassium phosphate monobasic to 500 ml volumetric flask, dissolved, and diluted to volume with water and adjusted to pH 4.8 + 0.1.

Figure 4.

Calibration curve for gatifloxacin fluorescence.

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Instrument Fluorescence spectra (Ex/Em) were collected at 25 + 18C using spectrofluorometer (Shimadzu RF-1501) with Xenon Lamp and 10 mm quartz cell. An Orion Ross combination pH electrode (Model 81 –02) was used for all pH measurements.

Preparation of Gatifloxacin Calibration Standards for Fluorimetry A stock solution of gatifloxacin was prepared by dissolving 10 mg in 25 ml 0.1 mmol l21 phosphoric acid and completed up to volume (100 ml) with potassium phosphate monobasic (pH 4.8). Serial dilutions were prepared from the stock solution to cover the range 16.0 – 80.0 ng ml21 using the same buffer (phosphoric acid/potassium phosphate monobasic). The calibration graph was constructed by plotting gatifloxacin concentration against fluorescence intensity.

Preparation of Gatifloxacin Sample Solutions for Fluorimetry An accurate weight of the powdered tablets equivalent to 12 mg gatifloxacin was transferred to a 100 ml volumetric flask, 25 ml of 0.1 mol l21 phosphoric acid was added and the solution was shaken with mechanical shaker for 10 min. The volume was completed with potassium phosphate monobasic buffer (pH 4.8 + 0.1) and filtered. The first 20 ml of the filtrate was rejected and 10 ml aliquot of the filtrate was transferred to 100 ml volumetric flask and the procedure was completed as previously mentioned. The same procedure was repeated using the standard addition technique and the unknown concentration of gatifloxacin in the tablets was calculated. Table 1.

Fluorimetric determination parameters of gatifloxacin

Parameters Concentration range, ng ml21 Recovery % + SD (authentic sample) Recovery % + SD (tablets) Recovery % + SD (added authentic) L.L.D., ng ml21 L.L.Q., ng ml21

Results 16 – 120 100.81 + 1.53 98.64 + 2.88 100.63 + 1.62 3.97 13.25

Comparison of the proposed methods with the reported methods for determination of gatifloxacin

Method LC with Column switching & fluorescence detector HPLC UV l286nm in pH 7.4 l286nm in pH 1.2 Fluoresence (lexc ¼ 292 nm & lem ¼ 484 nm) Micelle-enhanced spectrofluorimetry Fluorescence (lexc ¼ 291 nm & lem ¼ 495 nm)

Range

L.L.D

L.L.Q

Authors

162.5 – 5000 mg ml21

120 mg ml21

162.5 mg ml21

(Nguyen et al. 2004)

4 – 4 g ml21 1– 18 mg ml21 1– 14 mg ml21 0.04 –0.7 mg ml21

0.13 mg ml21 0.103 mg ml21 0.099 mg ml21 10 ng ml21

0.39 mg ml21 0.312 mg ml21 0.3 mg ml21 0.03 mg ml21

(Santom et al. 2006) (Venugopal and Saha 2005)

0.040 – 0.700 mg ml21

0.020 mg ml21

0.450 mg ml21

(Ocana et al. 2005)

0.016 – 0.120 mg ml21

0.004 mg ml21

0.016 mg ml21

This study


Table 2.

(Ocana et al. 2005)

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RESULTS AND DISCUSSION Specrofluorimetry Spectral Characteristics of Gatifloxacin Gatifloxacin in presence of 2.5 mmol l21 potassium phosphate monobasic solution was found to display a maximum emission at 495 nm when excited at 291 nm (Fig. 2). The fluorescence of gatifloxacin in different solvents and in presence of different pH buffers was studied. It was noticed that the fluorescence is pH dependent. At basic pH, the fluorescence was inhibited, whereas at acidic pH the fluorescence was enhanced. High intensity has been obtained in presence of phosphate buffer of pH 4.8 (Fig. 3). Stability of Fluorescence Signal High and stable fluorescence signal for up to 30 min was obtained upon using 2.5 mmol l21 potassium phosphate monobasic solutions (pH 4.8). Calibration Curve and Concentration Range A linear relationship between the fluorescence intensity (F) at 495 nm and the concentration of gatifloxacin in the range of (16 to 80 ng ml21) has been obtained (Fig. 4). A calibration graph was plotted and the line was characterized by a slope of 11.86 and y-intercept of 23.245 with r2 of 0.9968. The regression equation was used to compute the concentration of gatifloxacin. Concentration of gatifloxacin (ng ml21) ¼ 0.0843F485 þ 0.237. Application The method was successfully applied for the determination of gatifloxacin in bulk with a mean percentage recovery of 100.81% + 1.53. In addition, the method also was applied for the determination of gatifloxacin in Tequin Tablets 400 mg without interference from the pharmaceutical additives. The standard addition technique was tested and the mean percentage recoveries of 98.64% + 2.88 & 100.63% + 1.62 were obtained for tablets and added authentic drug (Table 1).

CONCLUSIONS It can be concluded that gatifloxacin can be direct fluorimetrically determined at sub ppm range without either extraction or concentration. The method provides a rapid, sensitive, and simple method for determining gatifloxacin in pure, authentic and aqueous media as well.


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