Development of Sٍٍensitive Spectrofluorimetric Methods for Determining Netilmicin Based on Selective Condensation Reactions of its Amine Moiety with each Acetylacetone/Formaldehyde and Ninhydrin/Phenylacetaldehyde Reagents.

Netilmicin is an aminoglycoside antibiotic used to treat infections caused by a broad spectrum of Gram-negative and Gram-positive bacteria and is pharmaceutically formulated in ophthalmic dosage forms. In this study, two spectrofluorimetric approaches were designed and developed to switch-on the fluorescence activity of NTC. The first method, or Hantzsch (HNZ) method, was relied on measuring the generated fluorescence intensity upon the condensation of NTC with acetylacetone and formaldehyde (Hantzsch reaction) at λemis=483 nm/λexcit=425.5 nm. While the second fluorometric method (NHD method) was relied on measuring the generated fluorescence intensity upon the condensation of NTC with ninhydrin/phenylacetaldehyde at λemis=482.2 nm/λexcit=385.8 nm. The reaction conditions for the two approaches were well investigated and optimized. The selectivity study for the methods was investigated by determining NTC in the presence of the co-formulated drug (dexamethasone) and pharmaceutical excipients. The validation for two approaches was performed based on ICH guidelines, and ranges of linearity were 0.1-1.2 and 1.5-6.0 µg/mL, while LOD values were 0.039 and 0.207 µg/mL for the HNZ method and the NHD method, respectively. Finally, NTC has been determined in different ophthalmic preparations by the proposed approaches with adequate recovery values.