Reserpine is a specific compound. Essential oil is natural extract which is obtained from hydrodistillation from a large variety of plant and contains many compounds. Which mean there is no reserpine essential oil. You have to select a particular essential oil which contains reserpine in large amount, and calculate the volume needed to obtain 64 mg of reserpine and dilute it in 1ml of your solvant.

First step choose your essential oil of reference

second step calculate the mass titration of reserpine in your selected essential oil (be careful titration in components of essential oil varies from one production to the next so you have to recalculate everytime you choose a new sample)

Otherwise you can choose to dilute pure reserpine (which is available as tablets i think) in your solvent of reference, but that won't be reserpine as a component of a specific essential oil.

Thanks Dear jean. This is helpful.

Thanks Dear jean. This is helpful.