In AZ this is the Dept of Weights and Measures. Probably has a similarly obscure name in the OP's state.

It might even say right on the gas pump - I think they put an inspection sticker on the pump showing the date it was last certified.

first thing is what station did you buy from.... im in houston as well.

food for thought gasoline is formed from petroluem distillate only the vapor burns from emitted gasoline liquid once its reached its vapor point it will no longer become a vapor temp and baro pressure regulate this. the liquid left behind will be an oily residue. this is not the proper way to detect contaminated fuel. the only way is to send off a sample to a testing facility and let them do a knock test and chemical breakdown...

Occam's razor suggests that the two most likely liquid contaminants are water and ethanol. If there is no visible sediment (particles) then the shop can test for those without even sending the fuel out, it takes a few minutes.

A side note, but I agree that it isn't worth calling the department of weights and measures. They typically worry about how much fuel is dispensed, not what that fuel consists of, in my experience.