Spectrophotometric and Atomic Absorption Spectroscopic Determination of Some Fluoroquinolone Antibacterials by Ion-pair Complex Formation with Bismuth (III) Tetraiodide

Abstract

New simple spectrophotometric and atomic absorption spectrometric (AAS) methods have been developed for the determination of levofloxacin (I), norfloxacin (II), and ciprofloxacin (III) in pure form, tablet formulations, and spiked human urine. The methods are based on the formation of ion-pair associates between the drugs and the inorganic complex, bismuth (III) tetraiodide. The reaction occurs in acidic medium to form orange-red ion-pair associates which are instantaneously precipitated. The formed precipitates are then filtered off and the residual unreacted metal complex in the filtrate is determined either spectrophotometrically at 453 nm or by AAS at 223.1 nm. Also, the precipitates may be dissolved in acetone and quantified spectrophotometrically at 469 nm or decomposed by hydrochloric acid, and the bismuth content is determined by AAS at 223.1 nm. The methods permit the determination of the three studied drugs in the range of 5–80 μg mL−1. The proposed methods were successfully applied to determine these drugs in their tablet formulations and spiked urine samples without any evidence for interference from pharmaceutical additives or biological matrix. The results were in good agreement with those obtained by the reference methods. The proposed methods, especially if automated, can be confidently applied for quality control and routine analysis of the studied drugs.