How can separate samples of optical isomers be distinguished?
By their rotation of plane-polarized light.
Given separate quantities of
Lanthanide shift reagents could be used to obtain the NMR spectra of the enantiomers (these would give a diastereomic spectrum because of the chiral shift reagent), though this is another specialized experiment.
What do you think would be the action of chiral medicines and drugs on our biochemistry?
See this older answer for details on the separation of optical isomers.