Citation:

Casey, J., S. Jackson, J. Ryan, AND S. Newton. The use of gas chromatography – high resolution mass spectrometry for suspect screening and non-targeted analysis of per- and polyfluoroalkyl substances. JOURNAL OF CHROMATOGRAPHY A. Elsevier Science Ltd, New York, NY, 1693:463884, (2023). https://doi.org/10.1016/j.chroma.2023.463884

Impact/Purpose:

PFAS have been of interest due to their environmental longevity (known as "forever chemicals"), tendency to bioaccumulate, and concerns regarding public and environmental health. PFAS exposure has been linked to cancer, heart disease, birth defects, and infertility3-6. PFAS compounds have been discovered in a variety of different commercial and industrial products such as: firefighting foam, non-stick cookware, cleaning products, takeout containers, etc. PFAS is often found in locations involved in the manufacturing, use, and/or disposal of these products. Locations where large concentrations of PFAS have been detected have been waste landfills, industrial centers, wastewater treatment plants, military and airbases7. PFAS have been detected in soil and water samples near these locations 8, 9. Furthermore, incineration has been used to dispose of PFAS but little research has been conducted to identify products of incomplete combustion when PFAS are incinerated. In the current study, a GC-HRMS spectral database was constructed using 141 PFAS. The custom PFAS database contain various types of spectra from the analysis of PFAS using electron ionization (EI) and chemical ionization (CI) mass spectrometry (MS). In creating this database, many observations were made involving ionization behavior of PFAS, characteristic fragmentations of PFAS, chromatographic behavior, etc. These observations were important in recognizing potential PFAS among unknown features in a sample data set. A workflow was created to select out likely candidate compounds in a feature (deconvoluted spectrum), to improve the accuracy and efficiency of identifying fluorinated compounds contained in a mixture. Additionally, a scoring system for GCMS was used from a previously reported study [22][23]. This scoring system was used to score PFAS and other fluorinated componds at different levels of confidence in a challenge sample and an incineration extract. The work presented here addresses issues regarding incinerated PFAS emissions into the environment and advances in methodology development in NTA GCMS.Implications for Environmental Analyses Numerous studies and reports continue to be published indicating increasing in levels of PFAS being released into the environment [30-33]. Many of these substances have yet to be identified and may be linked to biological and environmental health issues [34-37]. Many of these substances can traverse long distances (from evaporation/incineration) and redeposit in different food production sources, fisheries, and water drinking supplies[38-41]. In addition to investigating PFAS, other potentially harmful volatile compounds could be investigated using GC-HRMS with NTA workflows. Different government, industries, and commercial entities use incineration for the elimination of unwanted products and substances. Some of the sources for incinerated waste being released into the environment include trash incineration, biological waste incineration, wildfires, urban fires, halogenated waste incineration, commercial engine exhaust, and industrial waste exhaust [42-48]. Given the versatility of NTA GC-HRMS, other areas could benefit from further development of the work presented here. The large amount of scientific literature, news reports, and accounts of PFAS entering and increasing in concentration in the environment makes this study relevant and urgent [49-51]. As these issues become better understood, it is likely the interest, research, and regulation surrounding PFAS and other toxic compounds will continue to grow.

Description:

This study is a workflow development for the analysis, identification, and categorization of per- and polyfluoroalkyl substances (PFAS) using gas chromatography-high resolution mass spectrometry (GC-HRMS) with non-targeted analysis (NTA) and suspect screening techniques. The behavior of various PFAS in a GC-HRMS was studied with regards to retention indices, ionization susceptibility, fragmentation patterns, etc. A custom PFAS database was constructed from 141 diverse PFAS. The database contains mass spectra from electron ionization (EI) mode, as well as MS and MS/MS spectra from positive and negative chemical ionization (PCI and NCI, respectively) modes. Common fragments of PFAS were identified across a diverse set of 141 PFAS analyzed. A workflow for suspect screening of PFAS and partially fluorinated products of incomplete combustion/destruction (PICs/PIDs) was developed which utilized both the custom PFAS database and external databases. PFAS and other fluorinated compounds were identified in both a challenge sample (designed to test the identification workflow) and incineration samples suspected to contain PFAS and fluorinated PICs/PIDs. The challenge sample resulted in a 100% true positive rate (TPR) for PFAS which were present in the custom PFAS database. Several fluorinated species were tentatively identified in the incineration samples using the developed workflow.

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