Determination of Venlafaxine and Modafinil in Individual Tablet Dosage Forms using Single RP-HPLC Method

Purpose: To develop a simple and selective isocratic method for the determination of venlafaxine and modafinil in tablet dosage forms.
Methods: The compounds were analyzed on Waters symmetry C18 column (4.6 mm x 250 mm i.d, 5µm) using a mobile phase consisting of a mixture of ammonium acetate buffer (pH was adjusted to 4.0 with glacial acetic acid):10 % methanol in acetonitrile, in the ratio of 60:40. The flow rate was 1.0 ml/min and column effluents were monitored at 225 nm. The method was validated according to ICH guidelines.
Results: Venlafaxine and modafinil were eluted with retention times of 4.416 min and 6.443 min, respectively. The method was linear in the range of 1.0 - 50 µg/ml for both venlafaxine and modafinil. The relative standard deviation (%RSD) was < 1 for both drugs while mean recovery values at different concentration levels were within limits. The performance of the method was not changed when small variations in the method were made.
Conclusion: The proposed method is accurate, reproducible and low-cost, and can be used for the routine analysis of the individual drugs in formulations.