Chiral Separation and Enantiomer Resolution (5C) Practice Test

A racemic drug is resolved by chiral HPLC into enantiomers E1 and E2. Only E1 is intended for clinical use. During stability testing at 37°C in aqueous buffer (pH 7.4), the isolated E1 sample shows a gradual decrease in optical rotation magnitude over 7 days, approaching zero, with no change in LC-MS mass. Based on these observations, which conclusion is most consistent with the results?

A chiral drug is administered as a racemate, but only the (S)-enantiomer binds a target receptor in vivo. A manufacturing team uses chiral HPLC to isolate (S) with 99% enantiomeric excess (ee) prior to formulation. If the final dose contains 100 mg total drug substance, what is most consistent with the meaning of 99% ee for this sample?