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Detection of D-Dopa in levodopa tablets by derivatization coupled with LC-MS/MS
Lei Ding1, Chundan Ye1, Junchen Zhu1
1State Key Laboratory of Advanced Drug Delivery and Release Systems, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang, China.
Journal of Chromatography. A
|August 16, 2025
Summary
A new method accurately detects trace amounts of the chiral impurity d-Dopa in Levodopa (L-Dopa) Parkinson's medication. This analysis is crucial for patient safety, revealing d-Dopa presence in commercial L-Dopa tablets.
Area of Science:
- Analytical Chemistry
- Pharmaceutical Analysis
- Chiral Separations
Background:
- Levodopa (L-Dopa) is a critical Parkinson's disease medication.
- Detecting chiral impurities like d-Dopa in L-Dopa is analytically challenging due to similar polarity.
- Existing methods struggle with the sensitive and selective quantification of d-Dopa.
Purpose of the Study:
- To develop a novel, sensitive, and selective analytical method for quantifying trace d-Dopa and other impurities in Levodopa.
- To assess the presence and levels of d-Dopa in commercial Levodopa formulations.
- To highlight potential safety concerns associated with d-Dopa contamination in Parkinson's treatments.
Main Methods:
- Chemical derivatization using a chlorine-labeled chiral probe (D-BPCl) to enhance detection.
- Analysis via liquid chromatography-tandem mass spectrometry (LC-MS/MS) on a C18 column.
- Validation of the method for sensitivity, linearity, recovery, and repeatability.
Main Results:
- The method achieved excellent chromatographic resolution (4.15) and high derivatization efficiency (97%) for d-Dopa and l-Dopa.
- Strong chiral selectivity was observed with D-BPCl, showing a 2.78-fold response ratio for d-Dopa over l-enantiomers.
- Detection limits were as low as 7.88 μg/L for d-Dopa and 9.85 μg/L for l-Dopa, with high linearity (R² > 0.99) and recovery (94.1–106.8%).
- d-Dopa was detected in 15 batches of Levodopa tablets (0.15–0.44%), indicating its likely generation during manufacturing.
Conclusions:
- The developed LC-MS/MS method provides a robust solution for the quantitative analysis of d-Dopa in Levodopa.
- The presence of d-Dopa in commercial Levodopa products raises significant safety concerns for Parkinson's patients.
- This study emphasizes the importance of stringent chiral impurity monitoring in pharmaceutical manufacturing.
