Testing pee that sat out

Whitney

I am 16 dpo and I’ve taken 3 tests so far that are BFN. I am going on 3 days past AF being due and no sign of it yet and my period is very regular. This morning I got up at 5am to pee but wanted to wait to take my test till I got up later. I peed in a cup and let it sit till 6:15am uncovered. When I got up again and got a BFN could the hcg have dissipated in this short window if there was any?