University of Khartoum

Optimization and Validation of Spectrophotometric Methods for Analysis of L-Dopa and L-Tyrosine in Pharmaceutical Formulation

Optimization and Validation of Spectrophotometric Methods for Analysis of L-Dopa and L-Tyrosine in Pharmaceutical Formulation

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Title: Optimization and Validation of Spectrophotometric Methods for Analysis of L-Dopa and L-Tyrosine in Pharmaceutical Formulation
Author: Basheir, Banan Elshiekh Elsied
Abstract: In this study optimization and validation of spectrophotometric methods for the determination of two pharmaceutical drugs containing amino group namely L-dopa and L-tyrosine in their pharmaceutical formulation were described. Three simple, accurate, precise, sensitive and rapid spectrophotometric methods were developed and validated. Method (A) was based on derivatization the amino group of L-dopa and L-tyrosine with7-Chloro-4-Nitrobenzoxadiazole (NBD-Cl) in alkaline medium at pH 12 and 9 forming colored productsat 544 and 388 nm respectively. Beer’s law was obeyed at ranges from 1 to 12 µg/mL for L-dopaand 10 to 50 µg/mL for L-tyrosine. The Limits of detection (LOD) were found to be 0.057 and 2.85 µg/mL and the limits of quantitation (LOQ) were found to be 0.17 and 8.60 µg/mLrespectively. Method (B) was based on the reaction of L-dopa and L-tyrosine with 1,2-Naphthoquinone-4-sulfonate (NQS) at pH 7.0 and 8.0, producing brown-colored products measured at 498 and 470 nm respectively. The calibration curves were linear over concentrations ranging from 5 to 30 µg/mL for L-dopa and from 5 to 25 µg/mL for L-tyrosine. The limits of detection were found to be 0.7 and 1 µg/mL and the limits of quantitation were found to be 2.3µg/mL 5.2 µg /mL for L-dopa and L-tyrosinerespectively. Method (C) was based on charge transfer between L-dopa and alizarin red (ARS) inethanol. The purple colored product showed a maximum absorption at 588 nm. The concentration obeyed Beer’s law from 10 to 60 µg/mL. Thelimit of detection was found to be 2.4 µg/mL. Different variables affecting the reactions were carefully studied and optimized. All three methods were validated with respect to accuracy, precision, linearity, sensitivity, limit of detection (LOD) and limit of quantitation (LOQ) according to the International Conference of Harmonization (ICH) guidelines for validation of analytical procedure. The proposed methods were applied successfully for determination of L-dopa and L-tyrosine in their pharmaceutical formulation. The percentages were found to be in range of 99- 94.8 and 98-94.5 for L-dopa and L-tyrosine respectively. The two drugs did not need any complex sample preparation such as extraction step prior to the drug analysis.
Description: 121page
URI: http://khartoumspace.uofk.edu/handle/123456789/18845
Date: 2016-02-10


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