Parabens project.

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Hi, i have a chemistry project due to next Monday (october 12), in our project we want to determine is parabens (a toxic compound) is present in daily products like toothpaste, makeup, lotions, etc. We are using ferric trichloride to determine if parabens if present in the product, first we dissolve the product we want to test in alcohol, then we soak a qtip in the alcohol and let it air dry until the alcohol evaporates and only the product is left, then in another container we put ferric thrichloride (liquid), when the qtip is dry we put a drop of ferric trichloride on a plate and dip the dry qtip in the ferric trichloride drop until it soak up the liquid, and after 1-10 minutes we are supposed to see a change in color in the qtip, but nothing happens, it's supposed to work because in the label of the product it says that it contains parabens, so it should change color, maybe we're doing something wrong, help please.

[norman40]

Hi luisspada,

I believe that the procedure you’ve described is the ferric chloride test for detecting the presence phenolic compounds. A paraben is one of a class of compounds that are derived from phenol. Some more information about parabens can be found here:

https://en.wikipedia.org/wiki/Paraben

Some phenolic compounds, including some parabens will give a color change with the ferric chloride test. But there are some phenols and parabens that will not react with ferric chloride. So one possible explanation for your result is that the paraben in the product you tested doesn’t react with ferric chloride.

The test procedure you described sounds OK. But you might try dissolving your test product in alcohol as you said in your post. Then add a drop or two of your ferric chloride solution directly to the alcohol solution. Perhaps you’ll see a color change in the solution within a few minutes.

I hope this helps. Please post again if you have more questions.

A. Norman