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

The Determination of Parkinson's Drugs in Human Urine by Applying Chemometric Methods

The spectrophotometric-chemometric analysis of levodopa and carbidopa that are used for Parkinson's disease was analyzed without any prior reservation. Parkinson's drugs in the urine sample of a healthy person (never used drugs in his life) were analyzed at the same time spectrophotometrically. The chemometric methods used were partial least squares regression (PLS) and principal component regression (PCR). PLS and PCR were successfully applied as chemometric determination of levodopa and carbidopa in human urine samples. A concentration set including binary mixtures of levodopa and carbidopa in 15 different combinations was randomly prepared in acetate buffer (pH 3.5).). UV spectrophotometry is a relatively inexpensive, reliable, and less time-consuming method. Minitab program was used for absorbance and concentration values. The normalization values for each active substance were good (r2>0.9997). Additionally, experimental data were validated statistically. The results of the analyses of the results revealed high recoveries and low standard deviations. Hence, the results encouraged us to apply the method to drug analysis. The proposed methods are highly sensitive and precise, and therefore they were implemented for the determination of the active substances in the urine sample of a healthy person in triumph.

Simultaneous determination of L-dopa and benserazide in binary mixtures using first derivative of the ratio-voltammetric methods based on their oxidation on solid electrode

The electrochemical behavior of L-dopa and benserazide at a solid electrode has been investigated using different voltammetric techniques. The anodic voltammetric characteristics of the selected compounds have been studied in aqueous media as a function of pH by cyclic, differential pulse and square wave voltammetric techniques. First derivative of the ratio voltammetric methods for determination of these compounds in their dosage forms in the presence of each other has been described. This technique depends on the measuring of the first derivative of ratio voltammograms of each concentration as a function of the increased concentrations. DP and SW voltammetric methods depend on the measuring of first derivative of the ratio voltammetry by measurements of the selected potentials corresponding to either maximums or minimums for both drugs. The linear response was within the range of 1 × 10–5–8 × 10–5 and 1 × 10–5 – 2 × 10–4 M for L-dopa and benserazide, respectively. The validity of the proposed methods was successfully assessed for analyses of both drugs in laboratory-prepared mixtures and in commercial tablet formulations. The proposed methods have successfully applied to the simultaneous determination of these compounds in the presence of each other.