The enantiomeric excess of a substance is a measure of how pure it is. In this case, the impurity is the undesired enantiomer (the "opposite-handed" mirror image of a chiral compound).
Read more about Enantiomeric Excess: Definition
Famous quotes containing the word excess:
“There is an excess both in happiness and misery above our power of sensation.”
—François, Duc De La Rochefoucauld (1613–1680)