No, you should filter for duplicate content before importing. It is not possible to do this on import in part because it is impossible to know if it in fact is a duplicate. A couple over simplified examples, suppose two people have the exact same name or business which have the same name but different addresses. It only gets vastly more complex the more variables you toss in in order to attempt to programmatically determine a duplicate or not which would make bulk importing on most web hosts not possible.
Sorry I do not have a better answer!