Quantitative determination of pefloxacin mesylate by residual-base neutralisation method

This work describes two procedures based on residual base determination for the quantification of pefloxacin mesylate (PFM) in bulk drug and in pharmaceutical products. In the first method involving titrimetry. the drug solution is treated with a measured excess of sodium hydroxide followed by back titration of The residual base with hydrochloric acid using a phenol red-bromothymol blue mixed indicator. The second spectrophotometric method involves treatment of a fixed amount of sodium hydroxide - phenol red mixture with varying amounts of the drug, and measuring the decrease in the absorbance of the dye at 560 nm. In the titrimetric method, a reaction stoichiometry of 1:1 was found in the quantification range of 4-20 mg of drug, The spectrophotometric method allows the determination of PFM in the 5-40 mug ml(-1) range. The molar absorptivity is 5.91 x 10(3) l mol(-1) cm(-1) and the Sandell sensitivity is 56.37 ng cm(-2). The methods were applied successfully to the determination of PFM in pharmaceutical preparations.