A Novel Sensitive Method for Quantitative Determination of Tobramycin by Spectrophotometer using Diphenylamine

  • Abdul Mannan Ophth Pharmaceutical Pakistan
  • Saima Asif Jinnah University for Women, Karachi
  • Khan Usmanghani Jinnah University for Women, Karachi


Objective: Tobramycin, which is an aminoglycoside antibiotic containing two aminoglycosidic units with the central scaffold of six membered cyclohexane ring. The -OH groups and -NH2 absorb electromagnetic radiation near lower wave length. Therefore, basicity, hydrophilicity and lack of a UV absorbing chromophore makes it challenging for detection by UV- visible detector of HPLC and spectrophotometer. Therefore,our study aims to present a simple and sensitive UV method for estimation of Tobramycin (TOB) in bulk and pharmaceutical formulations.

Method: For this purpose, we prepared derivative of tobramycin, diphenylamine acid was used as catalyst under high temperature during this experiment. Underdrastic conditions the glycosidic linkage opened and amino sugar unit becomes free (OHLA). The diphenylamine reacts with anmino sugar unit resulting in formation of enamine, which is a colored complex and absorbs EMR.

Result:The Tobramycin product showed absorbance at 635 nm with molar absorptivity 9.4 x 10-5mole−1.ml−1.cm−1.Optimization conditions for the derivatization were also investigated by HPLC.The procedure was valid because it did not show change in absorbance up to 7days.The percentage of recovery of TOB was 98.0 – 103 % with SD of less than 1% for both standard and samples.

Conclusion:  Thus, a simple, sensitive and efficient method was developed and validated for bulk and pharmaceutical analysis of Tobramycin.

Author Biographies

Saima Asif, Jinnah University for Women, Karachi

Faculty of Pharmacy

Khan Usmanghani, Jinnah University for Women, Karachi

Faculty of Pharmacy