A simple, robust and selective and sensitive spectrophotometric method has been developed for the determination of Ritonavir in pharmaceutical formulations. The method was based on the scanning of methanolic solution of the drug and methanolic solution of formulation. The method showed high sensitivity with linearity range from 10 to 20 μg/mL.

The lower limit of detection (LOD) was found to be 1.1 μg/mL and the limit of quantization (LOQ) was determined as the lowest concentration was found to be 3.3 μg/mL. The variables that affected the reaction were carefully studied and optimized. The proposed method was applied successfully for the determination of Ritonavir in pharmaceutical formulations. The percentage recovery was found to be 99.426 ± 0.59 (n = 9) for pharmaceutical formulation.

Calibration standards for ritonavir covering the range of 10-20 μg/mL were prepared by the method mentioned above and the serial dilutions were made with methanol. The calibration curve was obtained by plotting the intensity by absorbence of the ritonavir versus analyte concentration.

The slope and intercept of the calibration like was determined by linear regression using the least square method. Regression analysis of the calibration curve showed a linear relationship between the intensity of absorbence of ritonavir and the concentration with co-relation co-efficient higher than in all the curves assayed in pure form.