A New Kinetic and Thermodynamic Study of Spectrophotometric Method for Determination of Adrenaline in its Pharmaceutical Formulations

A simple kinetic and thermodynamic study of spectrophotometric method for the quantitative analysis of adrenaline (AD) in pure and pharmaceutical dosage forms has been performed. The method is based on the formation of a sensitive green complex between ferrous ion (resulting from the redox reaction between AD and ferric chloride) and nitroso-R-salt reagent (NRS). The increase in absorbance of the colored complex is followed spectrophotometrically at 712 nm as a function of time. The initial rate and fixed time techniques were adopted for constructing the calibration curves. The linearity ranges were found to be 0.5 - 10 and 0.1 - 8 mu g center dot mL(-1) for the initial rate and fixed time methods, respectively. Thermodynamic parameters, including the free energy change, enthalpy of formation, and entropy were determined for the reaction product. The method was applied successfully for the estimation of AD in commercial dosage forms with results in a good agreement with those obtained by the official method.