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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?

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  • $\begingroup$ Bad idea. If you have ethanol on your hand and touch the paper, you invite the bisphenol to diffuse into your skin. Buy from reputable sources, ask for test reports by reputable laboratories. $\endgroup$ – Karl Jan 4 at 21:10
  • $\begingroup$ No that testing method is meaningless. The darkening of the thermal paper is, as expected, from heat or friction of your fingers. Ask the manufacturer. $\endgroup$ – M. Farooq Jan 5 at 1:16
  • $\begingroup$ The problem with any test for BPA or related compounds is that it has to be sensitive to very small amounts and to be specific for those compounds. Simple test are unlikely to be reliable or robust. Plus the description of BPA as "toxic" is disputed, especially given that it is often claimed without the important quantification for any toxin of "what amount creates a notable effect". $\endgroup$ – matt_black Mar 7 at 14:43
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I agree with M. Farooq, a test that might work is cutting small pieces of thermal paper and placing them in a tube with grain alcohol or a facsimile, and allowing them to soak for a few hours, then send the sample to a lab and ask them to test for bisphenol A/S. If you can, it's just better to ask the company.

Edit: you can just soak them in grain alcohol. It's hard to do a specific test for bisphenols, but I found one for phenols in general.

Procedure:

  • Prepare a dilute solution of ferric chloride in grain alcohol.
  • Using an eyedropper, add a few drops of the solution to a teaspoon of your solution to test.
  • If a color change is observed, phenols are present.

This is not ideal, but it's the best you can do.

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  • $\begingroup$ thanks everyone. sending for a lab test is expensive. I want some makeshift testing procedure, though I understand it is not completely safe. I tried on several receipts. I found no spot appearing on BPS/A free thermal paper and spots do appear on BPA free thermal paper. $\endgroup$ – Anees Feb 4 at 20:12
  • $\begingroup$ thanks everyone. sending for a lab test is expensive. I want some makeshift testing procedure, though I understand it is not completely safe. I tried this idea on several receipts. I found no spot appearing on BPS/A free thermal paper, and spots do appear on BPA free thermal paper. can you please just confirm how do BPS/A react with 80% Ethanol? Should this leave any colored residue in chemical reaction? $\endgroup$ – Anees Feb 4 at 20:22
  • $\begingroup$ Check my answer, I updated it. $\endgroup$ – Jacob Feb 5 at 22:38

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