I'd define a new table for your "master set". I'd set up a unique values validation rule, with the validate always option enabled on this new table.
Then I'd import all records from your current table into this new table. The validation rule will filter out duplications during the import, permitting only one record for each unique value to be imported.
Note: this assumes that you are specifying unique values for a single field. If it is the combination of values from several fields that must be unique, a slightly more sophisticated set up is needed in order for this to work.