I'm not sure on this one but... a detergent that does not have UV brighteners in it does not necessarily mean that it will alsoeliminate UV brighteners previously applied to the fabric. There used to be a product that was sprayed on fabric to eliminate UV brighteners and you had to use UV free detergent in all subsequent washings to retain this.
Does anyone else know for sure if UVbrighteners can beWASHED out?