Kinetic-spectrophotometric determination of neomycin

A new kinetically-based spectrophotometric method for the determination of micro quantities of neomycin is described in this paper. It is an adaptation of the modified Berthelot method which is a widely used colorimetric procedure for urea determination. The method was developed due to neomycin effect on 2,2′-dicarboxyindophenol formation. The experimental conditions for successful determination of neomycin were optimized. The relative standard deviation (RSD) for the neomycin concentration interval of 77–154 μg/mL, ranges from 0.7 to 1%. The method was directly applied to determining neomycin in ophthalmic drops. The obtained results in analyzed pharmaceutical samples were in accordance with disc-diffusion microbiological method results.