Micellar HPLC-UV method for the simultaneous determination of levodopa, carbidopa and entacapone in pharmaceuticals and human plasma

A method based on micellar liquid chromatography to quantify levodopa, carbidopa and entacapone in plasma is reported. The sample pretreatment was a simple dilution in a pure micellar solution then filtration and direct injection, without requiring extraction or purification steps. The three drugs were resolved from the matrix in 7 min, using an aqueous solution of 0.1 M sodium dodecyl sulphate-10% n-propanol-0.3 tiethylamine, adjusted at pH 2.8 with 0.02 M orthophosphoric acid as mobile phase, running under isocratic mode at 1.0 mL/ min through VP-ODS column. The detection was done by UV (ultraviolet) absorbance at 225 nm. The method was successfully validated by the International Conference Harmonization guidelines in terms of: selectivity, linearity (r2 > 0.998) over the concentration ranges of 0.025-1.2, 0.05-1.0 and 0.3-2.0 μg mL−1 with limits of detection of 0.01, 6.16 × 10−3 and 0.02 μg mL−1 and limits of quantification of 0.03, 0.02 and 0.07 μg mL−1 for levodopa, carbidopa and entacapone, respectively. The proposed method was applied successfully for quantification of the studied drugs in their different dosage forms. Moreover, the method was further extensive to the quantification of the studied drugs in spiked human plasma and was successfully validated by the guidelines of the European Medicines Agency. The proposed procedures were successfully evaluated to determine the studied drugs in real human plasma. The procedure was found reliable, practical, cost-effective, available, short period, easy-to-handle, low-cost, environmental-friendly, secure, useful for the analysis of numerous samples per day. Lastly, the method was performed to the analysis of incurred, using quality control samples in the same analytical run, with adequate results. Therefore, it can be implementable for custom analysis in clinical laboratories.