Background: BPA and BPS (Bisphenol A/S) are artificial estrogens and therefore toxic chemicals for us. They are used in the coating of thermal paper. Thermal paper is used to print in-store receipts. There is a growing demand for thermal paper that is free of BPA and BPS for the health and safety of the public.
Question: how do we test it? I heard from someone that both BPS and BPA dissolve in ethanol. If we apply 80% Ethanol solution (commonly found in hand sanitizer) on the coating side of the thermal paper then it reacts (and dissolves) with BPS and BPA; as a result, you notice black and greenish-black spots start to appear on the paper. If the paper is free of BPS/A then no spot or marks will appear on coat-sided paper.
Is this method of testing correct? Does it at least give some accurate idea? What could you suggest for testing?