Colorimetric determination of gentamicin, kanamycin, tobramycin, and amikacin aminoglycosides with 2,4-dinitrofluorobenzene.

The reaction of 2,4-dinitrofluorobenzene (Sanger's reagent) is used to form colored products with aminoglycoside antibiotics. Stopping the progress of the reaction with acid after a fixed time allows aqueous solubility to be maintained while discharging any color due to excess reactant. The choice of an appropriate analytical wavelength results in adherence to Beer's law. Although this colorimetric method is not expected to be stability-indicating, it is convenient and should be useful in content uniformity determinations for pharmaceutical dosage forms (e.g., ointments).