A simple and sensitive spectrophotometric method was developed, optimized and validated for the determination of hydrazine in various drug substances. Which is the process genotoxic impurity. The validation of analytical method was realized trough specificity, linearity, Limit of detection, Limit of quantification, Precision and accuracy parameters. A model compound, Sitagliptin phosphate drug substance was chosen for this study and Limit of detection(LOD) and Limit of quantification(LOQ) values were 0.2 μg/g and 0.6 μg/g respectively. The average accuracy value is 97.8%-100.0%.And also determination of hydrazine in different drug substances like zinc carnosine, aprepitant. In zinc carnosine and aprepitant with slight modification in methodology were discussed in this work. The present work was aimed to develop a visible spectrophotometric method, which is simple, sensitive, accurate and cost effective to evaluate the quality of the bulk drugs.