Water quality analysis technology has advanced a lot in recent years, but it can still improve in the detection of some of the so-called emerging contaminants (chemical substances or materials that have recently been detected in water and whose presence may pose a risk. for the environment and human health) and, especially, in the identification of small quantities of perfluoroalkylated and polyfluoroalkylated substances (PFAS), perfluorinated organic chemical compounds used in the manufacture of a wide variety of consumer products.
A team led by engineers at the Massachusetts Institute of Technology (MIT, United States) has now designed a sensor that easily detects very small amounts of various types of PFAS, elements also known as “forever chemicals” because they do not decompose naturally and have been related to a variety of harmful health effects, including cancer, reproductive problems, and disruptions of the immune and endocrine systems.
Using new sensor technology, researchers showed they could detect levels of PFAS as low as 200 parts per billion in a water sample. The device they designed could offer a way for consumers to test their drinking water and could also be useful in industries that rely heavily on PFAS chemicals, including semiconductor manufacturing and fire equipment.
“There is a real need for these detection technologies. We're stuck with these chemicals for a long time, so we need to be able to detect them and get rid of them,” says Timothy Swager, John D. MacArthur Professor of Chemistry at MIT and senior author of the study. The results of this research have been published (March 12) in the journal PNAS, published by the United States National Academy of Sciences. Other authors of the paper are former MIT postdoc and lead author Sohyun Park and MIT graduate student Collette Gordon.
Compounds and materials containing PFAS chemicals are used in thousands of consumer products so their presence is growing. A known use of some PFAS is as enhancers of non-stick coatings for cookware, but these new compounds are also commonly used in water-repellent clothing, stain-resistant fabrics, grease-resistant pizza boxes, cosmetics, and foams. against fires, remember the developers of the new detection system.
Previous studies have confirmed that these fluorinated chemicals, which have been widely used since the 1950s, can be released into water, air and soil, from factories, wastewater treatment plants and landfills. Their presence may also be due to the wear and tear of the consumer products in which they are present.
In 2023, the U.S. Environmental Protection Agency set a “recommended health limit” for two of the most dangerous PFAS chemicals, known as perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonate (PFOS). These advisories require a limit of 0.004 parts per billion for PFOA and 0.02 parts per billion for PFOS in drinking water.
Currently, the only way a consumer can determine if their drinking water contains PFAS is to send a water sample to a laboratory that performs mass spectrometry testing. However, this process takes several weeks and is expensive.
To create a cheaper and faster way to test for PFAS, the MIT team designed a sensor based on lateral flow technology, the same approach used for rapid Covid-19 tests and pregnancy tests. Instead of a test strip coated with antibodies, the new sensor is embedded with a special polymer known as polyaniline, which can switch between semiconductor and conducting states when protons are added to the material.
The researchers deposited these polymers on a strip of nitrocellulose paper and coated them with a surfactant that can extract fluorocarbons such as PFAS from a drop of water placed on the strip. When this happens, the protons in the PFAS are attracted to the polyaniline and turn it into a conductor, reducing the electrical resistance of the material. This change in resistance, which can be precisely measured using electrodes and sent to an external device such as a smartphone, provides a quantitative measurement of the amount of PFAS present.
The current version of the sensor can detect concentrations as low as 200 parts per billion of PFBA and 400 parts per billion of PFOA. This is not low enough to meet current EPA guidelines, but the sensor uses only a fraction of a milliliter of water. The researchers are now working on a larger-scale device that could filter about a liter of water through a membrane made of polyaniline, and believe this approach should increase sensitivity by more than a hundred times, aiming to meet the objective. very low EPA advisory levels.
An easy-to-use, low-priced home device could be useful for analysis in cases where consumers have concerns about water quality. In some cases, if PFAS are detected in drinking water, relatively simple and affordable filters could also be used to reduce their presence but, in addition, it could serve to adopt preventive measures so that these contaminants do not reach the supply networks.
The authors of the new study indicate that their work could also be useful for manufacturers of products with PFAS, in the sense that they could be more attentive to the specific compounds that more easily reach the environment (and water, in particular) and thus reduce their use or replace them with safer ones.
