Science Buddies: "Ask an Expert"

For my science fair for honors chemistry, I am testing various plastics to see if they leach BPA. I am also testing each plastics melting point and density and seeing if there is any correlation between the two. I am currently trying to figure out how to test for BPA leaching.

An overview of my current procedures:
-fill bottles with a methanol-water solution and- let them sit for 24 hours/microwave for a few min (plan on doing both looking for difference)
-make an aqueous Iron (III) Chloride solution
-combine a few drops of the solution from the bottle with a few drops Iron (III) Chloride, look for reaction (ferric chloride reacts w/ phenol and turns purple)
-put combined solutions in a colorimeter and measure absorbance- (should change if color changes) this will quantify how much BPA is leached

To melt the plastics, our school lab has Vernier Melt Stations, which I plan on trying to use.

Another student I know who did BPA testing, used a spectrometer to detect BPA by measuring absorption; however, I'm not sure if this works out. He said he let a solution sit in the bottles (did not react them with anything) than he put them through the spectrometer at around 280nm and apparently he successfully found BPA.

Also, I am trying to contact nearby Universities to see if I could use a gas chromatography machine; which my research tells me is the best method. (However, I do not completely understand it, so if I can use one, I need to figure that out)

I have already tried to test the plastics for BPA (not for leaching) by putting them in hot water, then swabbing with acetone, then putting the swab in a drop of aqueous ferric choride and looking for a color change; however, I have yet to actually find BPA in something.


Does anyone have any suggestions for my lab as a whole? Any input would be wonderful.

Hello geneva,

You have chosen a challenging project. I did a very quick web search and found that most tests looking for BPA leaching from plastic bottles find very low concentrations. See for example, http://ehp03.niehs.nih.gov/article/fetc ... hp.0900604 and http://www.bisphenol-a.org/human/polyplastics.html.

I doubt that the phenol test applied to a test swab is likely to find such concentrations. You are likely to require the more sophisticated methods you mention. I'd suggest the following.

• Do a more thorough search to get an idea of what concentration you need to be able to see in your tests.
  Do a search to find the sensitivity of each available method.
  If, as I suspect, you need a spectrophotometer, a gas chromatograph or a mass spectrometer, ask around the biology and chemistry departments at universities and private research labs near you for some lab that would allow you to use their equipment. Such good-neighbor policies are not unheard of.

Another line of research would be to investigate methods to extract the bpa from the bottle. If you could find some way to collect all the BPA from a bottle into a small quantity of liquid, then the concentration would be much higher than to just swab the surface of the bottle.

Good luck, and let us know how it goes, WW