title: Simultaneous spectrophotometric determination of levodopa and carbidopa in pharmaceutical formulations and water samples by using mean centering of ratio spectra and H-point standard addition methods.
abstract: Two spectrophotometric methods are described for the simultaneous determination of binary mixtures of carbidopa and levodopa in pharmaceutical formulations, without prior separation steps, using the mean centering of ratio spectra and H-point standard addition methods (HPSAM). The methods are based on the difference in the absorption spectra for the products of the reaction of carbidopa and levodopa with 4-aminobenzoic acid in the presence of periodate ion at pH 4.0. The methods allow rapid and accurate determination of carbidopa and levodopa. The results showed that the methods were capable to simultaneous determination of 0.30-10.00 microg ml(-1) and 0.50-10.00 microg ml(-1) each of carbidopa and levodopa. The proposed methods were successfully applied to the simultaneous determination of carbidopa and levodopa in pharmaceutical samples.
authors.affiliation: Faculty of Chemistry, Bu-Ali Sina University, Hamadan, Iran. madrakian@basu.ac.ir
authors.forename: Tayyebeh
authors.initials: T
authors.lastname: Madrakian
authors.forename: Massoumeh
authors.initials: M
authors.lastname: Mohammadnejad
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry; D002230:Carbidopa / Q000032:analysis*; D007980:Levodopa / Q000032:analysis*; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D004364:Pharmaceutical Preparations; D007980:Levodopa; D002230:Carbidopa; D010129:4-Aminobenzoic Acid