Application of high-performance liquid chromatography for simultaneous quantification of levodopa, carbidopa, and benserazide in Parkinson’s drugs

Abstract

In this study, an analytical method was developed and validated to simultaneously determine the contents of levodopa (LD), carbidopa (CD), and benserazide (BZ) in pharmaceutical formulations used for the treatment of Parkinson’s disease by using high-performance liquid chromatography (HPLC) coupled with a diode array detector (DAD). The optimal chromatographic conditions were established using an HPLC mobile phase consisting of a 100 mM KH₂PO₄-H₃PO₄ buffer solution with a pH of 3.5 and an addition of 0.10 mM sodium 1-octanesulfonate (SOSF). The drug samples were prepared by dissolving them in a 100 mM H₃PO₄ solution to ensure complete solubilisation and stable chromatographic signals of the active ingredients. Under these optimised conditions, good sensitivity was demonstrated, with instrumental limits of detection (IDL) for LD, CD, and BZ determined to be 0.76, 0.19 and 0.38 mg/l, respectively. Precision was evaluated through intra-day and inter-day repeatability studies, with the relative standard deviation (RSD) values for both retention time and peak area consistently remaining below 4%, indicating high reproducibility. The validated method was subsequently applied to the analysis of commercial pharmaceutical tablets with recovery rates for LD, CD, and BZ ranging from 80 to 100%. The difference between the actual content determined by the HPLC-DAD method and the labelled content of the product was found to be less than 8%.