Author : Barry Mahdi. Mahood, Abdul
A Simple spectrophotometeric Assay for determination of L-Dopa in pharmaceutical preparations via oxidative coupling reaction.
journal of kerbala university,
Volume 5, Issue 1, Pages 49-59
A sensitive and simple spectrophotometric method for the estimation of levodopa (LDP) in either pure form or in its pharmaceutical formulation is described. The method is based on the reaction of levodopa with thiourea in the presence of ferric chloride as oxidative reagent , to form an intense blue – water solution dye that is stable and has a maximum absorption at 660 nm. A rectilinear relationship between absorbance and concentration range 2-32 g.ml-1 with a molar absorptivity of 2.027x103 L.mol-1 .cm-1 sandell sensitivity of 0.97x10-4 g.cm-2 , a relative error of ((-0.625)-3.06%) and a relative standard deviation(RSD) of(0.823-1.247%) depending on the concentration of levodopa . The detection limit of the method was found to be 0.349 g.ml-1. The stoichiometric ratio was found to be 1:1of Levodopa- Thiourea .The mole ratio was applied for determination of the conditional stability constant of the formed compound and was found to be 9.2x107L.mol-1. Finally, the proposed method have been applied successfully for the determination of levodopa in pharmaceutical preparations.