Analytical Sciences

Flow-Injection Spectrophotometric Determination of Azithromycin in Pharmaceutical Formulations Using p-Chloranil in the Presence of Hydrogen Peroxide

José Luiz RUFINO, Helena Redigolo PEZZA, and Leonardo PEZZA

São Paulo State University—UNESP, Institute of Chemistry of Araraquara, P. O. Box 355, 14801-970, Araraquara, SP, Brazil

A flow-injection (FI) spectrophotometric procedure exploiting merging zones is proposed for the determination of azithromycin in pharmaceutical formulations. The method is based on the reaction of azithromycin with tetrachloro-p-benzoquinone (p-chloranil) accelerated by hydrogen peroxide and conducted in a methanol medium, producing a purple-red color compound (λ_max = 540 nm). The FI system and the experimental conditions were optimized using a multivariate method. Beer's law is obeyed in a concentration range of 50 - 1600 µg mL^-1 with an excellent correlation coefficient (r = 0.9998). The detection limit and the quantification limit were 6.6 and 22.1 µg mL^-1, respectively. No interference was observed from the common excipients, and the recoveries were within 98.6 to 100.4%. The procedure was applied to the determination of azithromycin in pharmaceuticals with a high sampling rate (65 samples h^-1). The results obtained by the proposed method were in good agreement with those obtained by the comparative method at 95% confidence level.

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