OPK's

Can diluted pee cause a negative OPK? I'm thinking I'm very close to ovulation, so I took one with second morning urine today at 8:00 and another this afternoon (with a 2 hour hold). The first one in the morning was darker than the second one, but neither were positive. I'm wondering if the second one had diluted pee to make it even lighter than the first. Can this happen?