A simple innovative spectrofluorometric method for the determination of alendronate in bulk and in pharmaceutical tablets

Sodium alendronate is the first in a pharmacological class known as bisphosphonates, used for treatment of various bone diseases. Assay of bisphosphonates by a spectroscopic technique is very challenging due to the fact that they lack chromophores and none of them are fluorescent. In this work, a simple method is presented for determination of alendronate in bulk and in pharmaceutical tablets using spectrofluorometry by exploiting the ability of alendronate to displace salicylate from the iron(III)-salicylate chelate, forming a non-fluorescent colorless iron(III)-alendronate complex. The liberated salicylate is fluorescent and is equivalent to the mount of alendronate added. The response was linear over the concentration range 20-90 μM and the proposed method was validated according to the guidelines of the International Conference on Harmonization. The correlation coefficient was found to be 0.995 and the limit of detection was 7.5 μM. The method was successfully applied for determination of alendronate in the commercially available Osteonate® tablets. The average percent recovery ± percent relative standard deviation was found to be 102.118 ± 2.033 which is congruent with the label claim of the dosage form. The results were also compared to a reported method using t-test and F-test at 95% confidence level; no significant differences were observed. The presented method is simple, fast, easy, cost-effective and suitable for routine pharmaceutical analysis.