Novel approach for the determination of azithromycin in pharmaceutical formulations by Fourier transform infrared spectroscopy in film-through transmission mode

This work reports the development of a new method for the determination of azithromycin in pharmaceutical formulations employing Fourier transform infrared (FTIR) technique. The measurements were performed using a novel approach based on a film-through transmission mode. Several variables that could influence the analytical performance of the method were evaluated (solvent, nominal resolution, number of scans, mode of measurement and spectral region selected for measurement). Acetonitrile was the best solvent for the determination of azithromycin, employing the absorption band of the CO group at 1729 cm− 1. The extraction of azithromycin from the formulations was made by mechanical shaking of 25 mg of each sample with 1 mL of acetonitrile for less than 5 min. In the optimized conditions (8 cm− 1 nominal resolution and 25 scans per spectrum), the limit of detection in acetonitrile was 0.07 mg mL− 1 azithromycin. The method was applied to the determination of azithromycin in six commercial pharmaceutical formulations and recovery test, employed to evaluate the accuracy, provided recovery percentages in the range of 87-108%.