Fluorine detection in organic compounds

Many of you will know why I am asking this question. There is a lot of attention recently to the dangers of the so called Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS). In essence organic fluoropolymers with very attractive commercial properties like repelling grease, water and dust particles. Making them very wide spread in consumer products and the industry as a whole.

Unfortunately they tend to mimic normal organic compounds in the body and interfere with enzyme chains and other metabolic processes in multiple ways. Their extreme stability and slow expulsion rate cause them to bioaccumulate and easily reach dangerous levels in humans and in the environment. Looking at the health effects (discovered so far) they might be on par, if not more dangerous than ingesting unstable radioisotopes or heavy metals.

Since those compounds and their products are too varied for standard lab tests to be practical. My questions is:

Is there a way to chemically detect fluorine presence in solids and liquids? I understand that is likely very difficult at room temperature, but maybe enough heat will break the fluorine-carbon bonds and could expose F to specific reactions that could be easily observed?

To clarify I am looking for a practical inexpensive method I can perform safely at home. I would like to test multiple things like food containers, pizza boxes, shoes, etc. Precision and scientific level of certainty is not an issue, just an indication is what I need. I might be able to perform the heating in some kind of securely sealed heat and pressure resistant contained that could be put into a microwave or other heat source with all the reagents inside.

I just want an indication of Florine present at more than trace quantity, not search for PFAS specifically (which is way more complex)

I have very basic chemistry knowledge, so please excuse any mistakes I could have made in my question.

• Comments are not for extended discussion; this conversation has been moved to chat. Nov 7, 2021 at 21:17

Unfortunately, your analytical question is not an easy one, and no test can be done safely at home or by using a handheld gadget. The problem is fluorine, and tiny amounts of it in the sample. Fluorine in organic compounds does readily not participate in analytical detection tests.

A straightforward method for the qualitative detection of fluorine in organic compounds requires fusion with an alkali metal (Na, K), followed by fluoride ion detection via zirconium alizarin reaction. A color change from violet to yellow indicates the presence of fluorine in an organic compound. Microgram quantities can be analyzed, but this reaction is not at all friendly and safe!

You wish to analyze cardboard, food containers, pizza boxes, shoes…there is no universal solution test. The analytical methods will be based on the substrate you wish to analyze. For example, shoe analysis will be very different from cardboard analysis in terms of sample preparation. Someone will need to develop an extraction method for each sample followed by gas chromatography-mass spectrometry.

Alternatively, you will need an elemental analysis technique. Ordinary inductively coupled plasma mass spectrometry is not great for fluorine (small mass, buried in noise in the mass spectrum, and fluorine does not want to lose an electron and go into a mass spectrometer). So fancy approaches are needed, like the one reported here High-Sensitivity Elemental Mass Spectrometry of Fluorine by Ionization in Plasma Afterglow

Sadly, nuclear magnetic resonance is fundamentally insensitive, and so is any infrared-based method. So both techniques are useless for parts per million until and unless someone is willing to let run one sample for 24 hours to collect the signals. So if you still wish to check the linings of food containers, a lot of sample preparation is needed for infrared measurement and an expensive spectrum library for matching spectra.

In short consult the manufacturer of food items and/or consult a professional analytical service.

• Thanks a lot for the exhaustive reply @M. Farooq! I would like to clarify what do you mean by "Microgram quantities can be analyzed, but this reaction is not at all friendly and safe!" Nov 7, 2021 at 19:19
• Fusion with sodium or potassium results in converting the fluorinated organics to inorganic fluorides, which can then be detected via the wet chemical test described in the answer. But this is not something done outside a well equipped lab, with good working fume hood, PPE, etc.
– Ed V
Nov 7, 2021 at 20:17
• @BorisHamanov, Prof Ed already explained the fact that you cannot melt sodium with you sample outside a lab. I remember a very bad accident with my teacher in a university. She was demonstrating this fusion process and the hot burning piece of sodium flew from the small test tube and landed on her head. This is what I mean by not a safe test. Nov 7, 2021 at 22:12
• I am going to disagree with your NMR assessment here as $\ce{^19F}$ is a very strongly NMR-active nucleus on par with $\ce{^1H}$ and as fluorine is a single-isotope element. Furthermore, perfluorinated organic compounds have lots of fluorine atoms (as normal organic compounds have hydrogens) so they should be easily detected. However, NMR is not readily performed at home, I'll give you that.
– Jan
Nov 8, 2021 at 17:12
• Long time ago Scientific American used to publish experiments for amatuers. They had an experiment to make an NMR using Earth's field. Brilliant people of 70s. My perspective is from an analytical chemist's point of view. Our interest is often trace analysis. NMR is inherently insensitive due to Boltzmann's distribution as compared to other spectrometric techniques like mass spectrometers where parts per billion detection is not a problem. Basically I meant NMR is nowhere near any chromatographic detector in terms of sensitivity and speed. Nov 8, 2021 at 19:08