Photometric Determination of Famotidine by Its Change-Transfer Reaction with Alizarin Red

As studied by photometry,a complex with composition ratio of 1 to 1 was formed by the charge-transfer reaction between famotidine and alizarin red,having its absorption maximum at the wavelength of 525 nm.Linear relationship between values of absorbance and mass concentration of farmotidine was obtained in the range from 8.0 to 142.0 mg·L-1.Based on these facts,a method of photometric determination of famotidine was proposed and used in the analysis of drug samples of famotidine tablets and capsules for their famotidine contents,giving results in consistency with the labelled values.Tests for recovery were performed by standard addition method using these drug samples as matrixes.Values of average recovery found were 100.8% for the tablets and 99.6% for the capsules.The RSD′s (n=7) calculated from the measured values were 1.01% and 0.56% respectively.