Use of Charge Transfer Complex Formation Reaction in Spectrophotometric Microdetermination of Some Drugs

A spectrophotometric method is proposed for the determination of isoniazid, mesalazine,salbutamol and thymol drugs in their pure forms and in pharmaceutical preparations, based onthe charge-transfer (CT) complex formation reaction with o-chloranil as π-acceptor. Linearcalibration graphs were obtained in the concentration range 1-16 and 2-20 μg ml^-1 for isoniazid at 360 and 520 nm respectively, 1.25-30 μg ml-1 at 571.5 nm for mesalazine, 1.25-50 μg ml^-1 for salbutamol and 2.5-80 μg ml^-1 at 410 nm for thymol at room temperature. The molar absorptivity values are in the range 3460 and 14360 l.mol^-1.cm^-1 and the lower limit of detection limits are in the rang 0.1432-1.3164 μg ml^-1 for all the studied drugs. The stoichiometry of the drug- ochloranil complexes was found to be 1:1 except mesalazine which was found to be 1:2. No interference was observed from common pharmaceutical excipients. The procedure is characterized by its simplicity with accuracy and precision. The proposed method was applied successfully for the determination of the drugs in their pharmaceutical formulations.