Simultaneous Kinetic-Spectrofluorometric Determination of Levodopa and Carbidopa Using Partial Least-Squares Regression

• Published in: Analytical Sciences 2009/05/10, Vol.25(5), pp.633-638
• Main Authors: PAGANI, Ariana P., CABEZÓN, Miguel A., IBÁÑEZ, Gabriela A.
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Antiparkinson Agents - analysis; Carbidopa - analysis; Cerium - chemistry; Chemistry; Fluorescence; Hydrogen-Ion Concentration; Kinetics; Least-Squares Analysis; Levodopa - analysis; Oxidation-Reduction; Pharmaceutical Preparations - chemistry; Spectrometry, Fluorescence - methods; Sulfuric Acids - chemistry; Temperature
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.25.633

A simple and sensitive methodology for the simultaneous determination of levodopa and carbidopa in pharmaceutical samples is described. The method combines the advantages of fluorescence with partial least-squares (PLS) analysis, and requires no previous separation steps. The developed method is based on the oxidation of levodopa and carbidopa by cerium(IV) in a sulfuric acid medium and monitoring the fluorescence of the formed Ce(III) at λexc = 255 nm and λem = 355 nm. PLS uses differences in the reaction rates as a discriminatory parameter, and regresses the data of fluorescence vs. time onto the concentrations of the standards. Eight validation samples and seven commercial tablets were studied, using a nine-sample aqueous calibration set. The analyte recoveries from pharmaceuticals ranged from 98 to 101% for levodopa and from 100 to 108% for carbidopa. The results obtained by the developed method were statistically comparable to those obtained with high-performance liquid chromatography.