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A New Strategy for Detecting 'Eternal Chemicals'

At first glance, cardboard pizza boxes look harmless. Big slabs of dough, toppings and melted cheese should be retained from oven to table. Cardboard boxes biodegrade rapidly, making them ideal for single-use items. However, the inherent greasiness of pizza—and thus its deliciousness—means that the temporary paperboard house will become saturated with oil and look unsightly. A thin layer of greaseproofing on a pizza box seemed like the perfect solution, until scientists realized that the degreasing chemicals often used are perfluoroalkyl and polyfluoroalkyl substances, aka PFAS. In organic compounds, scientists have partially or completely replaced hydrogen atoms with fluorine. PFAS’ nearly unbreakable carbon-fluorine bond makes it ideal for firefighting foam, paints, clothing, food containers, and even dental floss.

However, the same chemical properties that have made PFAS so desirable to industry mean that these compounds accumulate in the body and environment. In recent years, researchers have linked his PFAS to a variety of health problems, including various types of cancer, immunosuppression, thyroid problems, low birth weight babies, and liver problems. Knowledge of the hazards of PFAS combined with improved testing methods means that consumers are pushing food manufacturers to reduce or even eliminate her PFAS. Following this concern, the U.S. Environmental Protection Agency (EPA) and the Department of Defense (DoD) have developed validated laboratory analytical methods for testing his PFAS in the environment such as wastewater, surface water, and soil. did. Of the 5,000 to 6,000 potential PFAS chemicals, EPA has developed criteria to test about 40 to date.

Choosing an appropriate analytical method

As awareness of PFAS contamination increases and detection techniques improve, scientists need to determine the best method to test for trace levels of PFAS in the environment. Additionally, these tests need to be quick, easy, and inexpensive so that they can be run at scale. Advances in PFAS testing promise to improve both scientific rigor and consumer safety.

Historically, chemists have used several strategies to identify and quantify specific PFAS compounds in environmental samples. Many techniques rely on the characteristic carbon-fluorine bond found in all his PFASs, but rarely found in the natural environment. The oldest technique is mass spectrometry (MS), which measures the mass of molecules by calculating their deflection due to a magnetic field. By combining the mass spectrometry capabilities of MS or tandem MS with an initial gas or liquid chromatography (LC) step for physical separation, researchers can analyze more complex mixtures of chemicals.

Choosing the right analytical method depends on both the specific PFAS chemicals that may be contaminating the sample and the sample itself. Most of the PFAS have short chains of 4-18 carbons in length. This makes it semi-aqueous and non-volatile, making it ideal for LC/MS. Improvements in instrumentation over the years have made LC/MS cheaper, more sensitive, and more suitable for a wider range of sample types.

test challenges

Replacing traditional PFAS chemistries such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) with newer alternatives also complicates the testing landscape. The vast range of potential PFAS chemicals and their precursors and degradation products in the environment means that the number of contaminants far exceeds known analytical standards. As a result, researchers developed a non-targeted screening method to identify novel His PFAS chemicals. Advances in quadrupole time-of-flight instruments have enabled researchers to screen a wider range of samples more quickly and efficiently than their traditional LC/MS.

Screening for PFAS compounds remains challenging, regardless of the method chosen. Their ubiquity in the environment—scientists have found his PFAS in polar bears living in the remote Arctic—means cross-contamination is a big problem.

PFAS are so ubiquitous that they can be found in common components of analytical instruments such as LC/MS, solvents, pipettes, vials, and collection bottles, used for testing, and subsequently giving rise to false positives. there is.

Sample preparation remains the most difficult part of analysis for many analytical chemists. This process is relatively straightforward for biological samples such as blood, serum and urine. For example, to measure her PFAS in her blood, acid is added to clot proteins. These can be spun down and the resulting liquid injected directly into the LC/MS or further processed to remove lipids. Solid tissue samples are often minced and enzymatically digested.

Environmental and food samples are more difficult. For example, dark lignin in sewage sludge and wetland water can interfere with MS and may require a charcoal wash after extraction. The vegetables should be chopped, salted, then spun down, resin added, and spun down again before injecting the sample. Fatty foods such as butter and some types of fish may also require solid phase extraction and cleanup.

Recent progress

Some of the biggest advances in PFAS analysis have been in sample preparation, not instrumentation. It doesn’t sound like a big improvement, but combining two resins into one cartridge saves a lot of money, time, and the potential for error. This is especially important for high-throughput labs processing 5,000-6,000 samples each month, and these new products can save you a lot of time. The sample preparation portion of the process has always been the biggest bottleneck for industry. This is the most time consuming and not always automatable.

Our new sample preparation technology not only saves you time, it saves you money. The more samples that can be processed, the lower the cost per sample. Sample preparation of water, tissue, food, and food contact materials remains a challenge, but incremental improvements will make it easier and faster to analyze samples, ultimately improving overall human health. It will be improved.

About the author:

Richard Jack is the Global Market Development Manager for Phenomenex’s Food and Environmental Division.