Development and Validation of RP-HPLC Method for the Estimation of Gemifloxacin Mesylate in Bulk and Pharmaceutical Dosage Forms

: A simple, rapid, accurate, precise and reproducible reverse phase high performance liquid chromatographic method has been developed for the estimation of gemifloxacin mesylate in bulk and pharmaceutical formulations. The quantification was carried out using cyberlab capcell pak, ODS C 18 (250 × 4.6 mm i.d., 5 µm particle size) column in an isocratic mode, with mobile phase comprising Buffer (KH 2 PO 4 with pH 6.8): acetonitrile in the ratio of 80:20 (%v/v).The flow rate was at 1.2 mL/min and the detection was carried out at 265 nm. The retention time of the drug was found to be 7.47 min and the method produced linear response in the concentration range of 25-150 µg/mL (R~0.99986). The recovery studies were also carried out and % RSD from reproducibility was found to be 0.82. The proposed method was statistically evaluated and can be applied for routine quality control analysis of gemifloxacin mesylate in tablets.


Figure 1. Chemical structure of gemifloxacin mesylate
Literature survey reveals that the drug can be estimated only by LC-MS/MS [4][5] and Chiral HPLC 6 in biological fluids and also by microchip electrophoresis 7 , chiral countercurrent chromatography 8 and colorimetric method 9 but no UV spectrophotometric method and HPLC method in pharmaceutical dosage forms have been reported so far.The present study describes a simple, sensitive, economical, accurate and precise HPLC method for the estimation of gemifloxacin mesylate in bulk and tablet formulation.
The objective of this study is to develop a simple, fast, selective, accurate, precise and sensitive RP-HPLC-UV method for the determination of gemifloxacin mesylate in bulk and in pharmaceutical dosage forms (tablets) suitable for routine quality control analysis.

Chemicals and reagents
Gemifloxacin mesylate bulk drug was received as gift sample from Orchid Chemicals and Pharmaceuticals Ltd., Chennai, India.G-cin-320 mg tablets, manufactured by Lupin Laboratories Ltd., Mumbai and Gemez-320 mg tablets, manufactured by Glenmark Pharmaceuticals Ltd., Mumbai, India were procured from local Pharmacy.HPLC grade water, methanol and acetonitrile were purchased from Merck, Mumbai, India.Potassium dihydrogen phosphate from S.d.fine chemicals ltd., India.

Instrumentation
The method development study was carried out isocratically on a high performance liquid chromatograph using Cyber Lab LC-100 separation module equipped with a rheodyne injector 7725i, single pump, 20µL fixed sample loop, 25 µL Hamilton syringe and detection was carried out using ultraviolet detector.Cyberlab digital balance was used for weighing purpose.

Optimized chromatographic conditions
Chromatographic separation was carried out at room temperature with Capcell Pak ODS C 18 (250 × 4.6 mm with 5 µm particles) column.Mobile phase containing buffer (KH 2 PO 4 adjusted with pH 6.8): acetonitrile in the ratio of 80:20 (%v/v), were filtered through 0.45 µ membrane filter and degassed in a sonicator for 10 min before use.The flow rate of mobile phase was maintained at 1.2 mL/min and detection was done using UV detector at 265 nm.The injection volume of both standards and samples were 10 µL (100 µg/mL).

Preparation of standard
A standard stock solution containing 1 mg/mL of gemifloxacin mesylate was prepared by completely dissolving 50 mg of pure drug of gemifloxacin mesylate in 50 mL of methanol in a 50 mL volumetric flask.A working standard solution containing 100 µg/mL was prepared by diluting 2.5 mL of stock solution (1000 µg/mL) into a 25 mL of mobile phase.YUNOOS MOHAMMAD et al.

Calibration curve of gemifloxacin mesylate
Linearity solutions ranging of 25-150 µg/mL of gemifloxacin mesylate were prepared from the above standard stock solution (1000 µg/mL) by diluting into a10 mL volumetric flasks with mobile phase.Initially the mobile phase was pumped for 30 min to saturate the column there by to get the baseline corrected as shown in Figure 2. Then solutions prepared as above were filtered through 0.45 µ membrane filter and then 10 µL of the filtrate was injected each time into the column at a flow rate of 1.2 mL/min.Evaluation of the drug was performed with UV-visible detector at 265 nm after the drug solution of 10 µg/mL in methanol was scanned in UV-visible spectrophotometer SL-164 in the range of 200-370 nm against methanol as blank and found λ max at 265 nm as show in Figure 3. Peak area was recorded for all the peaks.The plot of peak area vs. the respective drug concentration gives the calibration curve.The retention time of gemifloxacin mesylate standard was found to be 7.47 minutes as shown in Figure 4.

Analysis of gemifloxacin mesylate in tablet dosage forms
Twenty tablets each containing 320 mg gemifloxacin mesylate were accurately weighed and powdered.A quantity of the powder equivalent to 100 mg was taken into a 100 mL volumetric flask and 60 mL methanol was added.Then solution was sonicated for 10 min, dissolved and then made up to the volume with the methanol and filtered through a 0.45 µ membrane filter.Then 10 mL of the above filtrate was transferred into a 100 mL volumetric flask and diluted to the mark with mobile phase to obtain working standard solution of 100 µg/mL.Then 10 µL of the above solutions were injected each time into the column at a flow rate of 1.2 mL/min.The retention time of gemifloxacin mesylate samples were found to be 7.50 and 7.58 minutes as shown in Figure 5 and 6.

Results and Discussion
The present study was carried out to develop a simple, fast, accurate and precise RP-HPLC method for the analysis of gemifloxacin mesylate in bulk and in tablet dosage forms.For the determination of gemifloxacin mesylate, different compositions of mobile phases were employed.Initially, a mobile phase consisting of Methanol and Water in the ratio of 70:30 (%v/v) was tried where broad peak shape and more tailing was observed and a mobile phase consisting of acetonitrile and water in the ratio of 60:40 (%v/v) was tried where broad peak shape and less retention time was observed.Then the composition of mobile phase was changed to Phosphate buffer adjusted to pH 6.8 and methanol in the ratio of 70:30 (%v/v) but in these condition less retention time and broad peak shape was observed and a mobile phase consisting of phosphate buffer adjusted to pH 6.8 and acetonitrile in the ratio of 20:80 (%v/v) where less retention time and more tailing was observed.Similarly different trails were tried by adjusting compositions of buffer and acetonitrile but finally the ratio was changed to phosphate buffer adjusted to pH 6.8 and acetonitrile in the ratio of 80:20 (%v/v), where gemifloxacin mesylate was eluted at around 7.47 min with symmetric peak shape and shorter retention time.The results of system suitability parameters were given in the Table 1.

Method validation
Linearity was determined from calibration graph plotted using peak area response versus concentration of the standard solutions and it was found to be obeyed in the concentration range of 25-150 µg/mL with a good linear relationship (r=0.99986) as shown in Figure 7.
The regression curve was constructed by linear regression fitting and its mathematical expression was y=2984.56x -1864.33 (where y is the peak area and x is the concentration of gemifloxacin mesylate).

Development and Validation of RP-HPLC Method 1626
Precision of the developed method was studied by repeatedly injecting gemifloxacin mesylate standard and sample solutions for six times (n=6).The % RSD was found to be 0.82 and 0.78 respectively.The amount (%Assay) of gemifloxacin mesylate in two different brands of tablet dosage forms is shown in Table 2.The tablets were found to contain 99.64% and 100.09% of the drug.It can be concluded that the proposed RP-HPLC method is sufficiently sensitive and reproducible for the analysis of gemifloxacin mesylate in tablet dosage forms within a short analysis time.

Conclusion
In this present study an attempt has been made to develop RP-HPLC method for the determination of gemifloxacin mesylate in tablet dosage form.The results obtained were reproducible and reliable.The validity and precision of the methods were evident from the statistical and analytical parameters obtained.From the forgoing it is concluded that the method developed is simple, rapid, selective, economical, accurate and precise and hence suitable for application in routine quality control analysis of Pharmaceutical preparations.

Figure 7 .
Figure 7. Calibration curve of gemifloxacin mesylate.The drug content (Assay) in the tablets was quantified using the proposed RP-HPLC method.The amount (%Assay) of gemifloxacin mesylate in two different brands of tablet dosage forms is shown in Table2.The tablets were found to contain 99.64% and 100.09% of the drug.It can be concluded that the proposed RP-HPLC method is sufficiently sensitive and reproducible for the analysis of gemifloxacin mesylate in tablet dosage forms within a short analysis time.Table2.Results of assay in marketed formulation

Table 1 .
Results of system suitability parameters of gemifloxacin mesylate in standard and

Table 2 .
Results of assay in marketed formulation The recovery experiment was carried out by spiking the already analyzed sample of the tablets with their different known concentration of standard.The average percentage recovery was calculated and results are summarized in Table3.

Table 3 .
Results of Accuracy (Recovery studies, n=3) The developed method was validated according to the standard procedure and the summary of results obtained is presented in Table4.

Table 4 .
Summary of Validation Parameters S.No.