New Study Uses MSPE with GC–MS to Analyze PFCAs in Water

A study done by researchers from China University of Geosciences and Wuhan Textile University in Wuhan, China recently magnetic solid-phase extraction (MSPE) with gas chromatography–mass spectrometry (GC–MS) to analyze perfluoro carboxylic acids (PFCAs) in different water environments. Their findings were published in the Journal of Chromatography A (1).

Water pollution concept. Woman scientist takes a water sample from polluted pond. | Image Credit: © Natali - stock.adobe.com

PFCAs are a type of compound characterized by the presence of a carboxyl group and perfluoroalkyl chains, in which all hydrogen atoms are replaced by fluorine atoms. Part of the larger group of per- and polyfluoroalkyl substances (PFAS), these compounds are partially characterized by the high electronegativity and low polarizability of fluorine atoms, which give PFCAs strong hydrophobic and exceptionally low surface tension (2). Further, the carboxyl group enhances solubility of PFCAs in water. Due to their chemical stability, PFCAs have widespread use across different industries, including chemical, mechanical, textile, and paper sectors. PFCAs can enter the environment through industrial admissions, waste disposal practices, and consumer product use.

The resistance of PFCAs to degradation raises concerns about bioaccumulation and potential entry into the food chain, which could endanger wildlife and human health. Developing a simple, rapid, and efficient method for enriching and analyzing PFCAs in complex samples provides a notable opportunity for enhancing our understanding of PFCAs’ potential impact. A 2023 study found that at least 45% of the United States’ tap water held one or more types of PFAS, with the study testing for 32 types of PFAS (3). Since 1999, the National Health and Nutrition Examination Survey (NHANES), established by the Centers for Disease Control and Prevention (CDC), has measured blood PFAS in the U.S. population (4). Since 2002, production and use of PFAS in the United States have declined, lowering domestic blood PFAS levels.

In this study, scientists developed a novel magnetic mesoporous fluorinated metal-organic framework material (Fe₃O₄@MIP-206-F) specifically for application as an adsorbent for PFCAs extraction via magnetic solid-phase extraction (MSPE). The fluorinated mesoporous metal-organic framework MIP-206-F was synthesized by selecting ZrOCl₂ and 5-fluoroisophthalic acid (5-F-IPA) and subsequently loaded it onto amino-modified Fe₃O₄ to obtain Fe₃O₄@MIP-206-F. This compound features open metal sites of zirconium (Zr), F-functional groups, and amino-functional groups, making it an ideal adsorbent for PFCAs extraction.

MSPE is one of many effective sample pretreatment techniques used to extract and enrich PFCAs from samples. MSPE stands out due to its extraction efficiency, robust anti-interference capability, and minimal solvent consumption. Further, it facilitates convenient separation and recovery of solid-phase materials with applying its magnetic field, enabling efficient enrichment and isolation of target analytes. This process, which was combined with gas chromatography–mass spectrometry (GC–MS), was used to analyze six PFCAs in lake water and groundwater samples.

The Fe₃O₄@MIP-206-F material features porosity, open metal Zr and functional groups (fluorine and amino) conducive to the adsorption process. The adsorption methods involved include acid-base interactions, hydrophobic interactions, F-F interactions, electrostatic interactions, and size complementarity. By optimizing key parameters, MSPE’s extraction efficiency was improved.

By combining MSPE with GC–MS, a rapid, simple, and sensitive method for analyzing PFCAs was established. The developed method showed a wide linear range (0.050–50 ng mL⁻¹), low detection limits (0.0010–0.0019 ng mL⁻¹), good recoveries (86.7 % to 111 %), and intra- and inter-day precision.

References

(1) Liu, H.; Di, S.; Liu, Y.; Li, Z.; Chen, P.; Zhu, S. Magnetic Fluorinated Mesoporous Metal-Organic Frameworks for Rapid Derivatization-Assisted GC–MS Analysis of Perfluoroalkyl Carboxylic Acids in Harsh Water Environment. J. Chromatogr. A 2025, 1741, 465612. DOI: 10.1016/j.chroma.2024.465612

(2) Patel, R.; Saab, L. E.; Brahana, P. J.; Valsaraj, K. T.; Bharti, B. Interfacial Activity and Surface pKa of Perfluoroalkyl Carboxylic Acids (PFCAs). Langmuir 2024, 40 (7), 3651–3658. DOI: 10.1021/acs.langmuir.3c03398

(3) Tap Water Study Detects PFAS ‘Forever Chemicals’ Across the US. USGS 2023. https://www.usgs.gov/news/national-news-release/tap-water-study-detects-pfas-forever-chemicals-across-us (accessed 2025-1-20)

(4) Fast Facts: PFAS in the U.S. Population. PFAS and Your Health 2020. https://www.atsdr.cdc.gov/pfas/data-research/facts-stats/index.html (accessed 2025-1-20)