A novel spectrophotometric method for determination of modafinil in pharmaceutical formulations using quinalizarin

Simple, extraction free visible spectrophotometric method was developed and validated for the quantitative estimation of modafinil in pharmaceutical formulations and bulk drug using quinalizarin as analytical reagent. The method involve the reaction of modafinil with quinalizarin in alcoholic medium at room conditions to form a blue colored product exhibiting maximum absorption at 572 nm. Different variables affecting the reaction were studied and optimized. Under the optimized experimental conditions, Beer's law is obeyed in the concentration ranges of 20-180 μg.mL‾ˡ with the detection of limit value of 0.258 μg.mL‾ˡ for the method .The molar absorptivity for the method was reported. The method was validated in terms of accuracy, precision and robustness,the results were satisfactory. The proposed method was effectively applied to the analysis of the modafinil in their tablet formulations. Recovery studies for modafinil was found to be 99.9% . The %RSD value was found to be 0.6% for the method. The assay was not interfered by common excipients.