Danny, welcome to the forum.
Almost 6 years later ...
Unfortunately, the link given is broken. But, this one now works:
Get PDF - Determination of levodopa by capillary zone electrophoresis using an acidic phosphate buffer and its application in the analysis of beans
It is still behind a pay wall.
Regarding the determination of levodopa in lentils I would now suggest spectroscopy. There's many "citizen science" articles about the technique.
John