What do you exactly mean with analytical and pharmaceutical drugs?

The drug permeation into the cell depends on the molecule structure/ functional Groups.

what kind of drugs are you thinking of using?

Thanks Mr EI-Hage.

There are different cat. numbers for a drug in Sigma Aldrich for technical, pharmaceutical and analytical grades.

They have various related category with similar molecular weight.

I have bought technical grade for my project, but I worry about different function of this drug in cell culture.

Doesn't really matter as long as the form you are using is pure (normally >99%) and bio-available. Either grade is fine the drug is the drug obviously for certain methods like HPLC contaminants may be a problem. The main thing is  will it go into solution in your culture medium at the concentration you want to use it, which may dictate whether you but a base or salt form of the drug. In genrral you want to minimise the need or amounts of adding organic solvents to your media (EtOH, DMSO, DMF).

Thanks a lot.