Sassafras oil cant be concentrated anymore than it is. It could be fractionally distilled to collect the componts of the crude oil in a certain boiling range.
If the sassfras concentrate you are looking at is labled as a food flavor addative than its artificial sassy and contains no safrole. There is a nitche market for sassafas flavoring in the gourmet candy industry and you can purchase a sassafras addative, but to my experiance these contain no safrole.