New, simple and cost effective UV-spectrophotometric methods were developed for the estimation of gatifloxacin in bulk and pharmaceutical formulations. Gatifloxacin was estimated at 286 nm in 100 mM phosphate buffer (pH 7.4) and 292 nm in 100 mM hydrochloric acid (pH 1.2). Linearity range was found to be 1-18 mug ml(-1) (regression equation: absorbance=0.0684 x Concentration in microg ml(-1) + 0.0050; r2 = 0.9998) in the phosphate buffer (pH 7.4) and 1-14 microg ml(-1) (regression equation: absorbance = 0.0864 x Concentration in microg ml(-1) + 0.0027; r2 = 0.9999) in hydrochloric acid medium (pH 1.2). The apparent molar absorptivity was found to be 2.62 x 10(4) l mol(-1) cm(-1) in the phosphate buffer and 3.25 x 10(4) l mol(-1) cm(-1) in hydrochloric acid media. In both the proposed methods sandell's sensitivity was found to be about 0.01 microg cm(-2)/0.001A. These methods were tested and validated for various parameters according to ICH guidelines and USP. The quantitation limits were found to be 0.312 and 0.3 microg ml(-1) in the phosphate buffer and hydrochloric acid medium, respectively. The proposed methods were successfully applied for the determination of gatifloxacin in pharmaceutical formulations (tablets, injection and ophthalmic solution). The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation <2%), while being simple, cheap and less time consuming and can be suitably applied for the estimation of gatifloxacin in different dosage forms and dissolution studies.
"The chemical structure of GTF is shown in Figure 1 . There are some reports in the literature regarding the determination of GTF by high-performance liquid chromatography (Overholser et al. 2003 , Salgado and Lopes 2006 ), spectrophotometry (Venugopal and Saha 2005 , Amin et al. 2007 , Darwish et al. 2010 ), spectrofl uorimetry (Ocana et al. 2005 , Guo et al. 2009 ), high-performance thin-layer chromatography (Motwani et al. 2006 ) and voltammetry/polarography (Ries et al. 2005 , El -Desoky 2009 , Ramadan and Mandil 2010 ). However, there is no report in the literature regarding the determination of GTF using carbon nanotube paste electrode , although the electrochemical method has many advantages such as its high sensitivity, rapid response, low cost and simplicity. "
[Show abstract][Hide abstract] ABSTRACT: The electrochemical oxidation of an antibacterial drug, gatifloxacin (GTF), at multi-walled carbon nanotube paste electrode was studied employing cyclic and differential pulse voltammetry methods. The effect of scan rate, pH, different electrolytes, pulse amplitude and accumulation time on electrochemical behavior of GTF were investigated. GTF shows a well-defined oxidation peak at +1.05 V in acetate buffer of pH 5.0 +/- 0.01. Under optimized conditions, the peak current is linear over the concentration range 2.13x10(-5)-1.7x10(-4) M with detection limit of 4.5x10(-9) M. The applicability of the proposed method is further extended to in vitro determination of the drug in biological fluids. Differential pulse voltammetry and UV-VIS absorption techniques were employed to probe the interaction between GTF and calf thymus DNA. The addition of ds-DNA to the analyte containing GTF results in a decrease of the peak current and a positive shift of the peak potential of GTF in differential pulse voltammetry analysis, indicating the dominance of the intercalating interaction. The spectroscopic data also confirm the interaction between GTF and ds-DNA. The combining constant (beta) and combining number (m) of GTF-mDNA were also determined.
[Show abstract][Hide abstract] ABSTRACT: A new, simple, and sensitive ion-pair reverse-phase liquid chromatographic method is developed and validated for the estimation of 1-cyclopropyl-6-fluoro-8-methoxy-7-(3-methylpiperazin-1-yl)-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (gatifloxacin) in bulk and formulations using a UV detector under isocratic conditions. The selected mobile phase consists of the aqueous phase (a 25 mM citrate buffer comprising of 10mM cationic and anionic pairing agents, pH adjusted to 3.5) and acetonitrile (52:48%, v/v). The selected wavelength is 292 nm. Retention time of gatifloxacin is 5.2 min. The linearity range is found to be 50 to 1000 ng/mL (the regression equation is area = 105.5 x concentration in ng/mL--695.8), and the regression coefficient is 0.9996. Validation results demonstrate accuracy, precision, and reproducibility (relative standard deviation < 3%) of the method. The detection and quantitation limits are found to be 6.50 and 17.38 ng/mL, respectively. The method is successfully used for the estimation of gatifloxacin in a variety of dosage forms, and the results are in good agreement with the label claims.
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