MSACL 2023 Abstract

PFAS in Me: Which Ones and How Much?! Karl Oetjen (1), Andrew Patterson (2), Thep Phomsopha (2) (1) SCIEX, USA (2) Eurofins, Sacramento, CA Karl Oetjen, PhD (Presenter) SCIEX

Presenter Bio: Karl Oetjen is a Senior Scientist at SCIEX in the technical marketing group and has over 10 years of mass spectrometry experience. Before joining SCIEX, he completed his PhD at Colorado School of Mines (Golden, Colorado) in Hydrologic Science and Engineering under Dr. Chris Higgins. Karl’s dissertation research focused on nontarget characterization of complex surfactant mixtures, including aqueous film forming foams. This work led to the discovery of several novel per- and polyfluorinated alkyl substances (PFAS) that have since been found in various environmental samples and industrial chemicals. Since joining SCIEX, Karl has worked with numerous labs creating and implementing both regulated and unregulated quantitative and qualitative screening methods

Introduction:
Bioaccumulation of PFAS in the human body resulting from environmental exposure is a growing public health concern. Recent studies have linked PFAS exposure to adverse health outcomes including childhood health complications, reduction in kidney functions, thyroid disease, hormone suppression, decreased fertility, increased cholesterol levels, and diabetes, among others. Given the prevalence and ubiquitous nature of PFAS in the environment and every-day consumer products (including our drinking water supply), there is a critical need to develop quantitative tools capable of accurately and precisely detecting low-levels of PFAS in biological fluids in order to understand the impact on the human body.

In this study, we combined low volume blood sampling with the SCIEX QTRAP 7500 system for the analysis of trace level of PFAS. We present here a quantitative workflow capable of accurately quantifying sub-ng/mL levels of 42 PFAS compounds. The analysis was performed on the author and the results of the analysis are shared to demonstrate what PFAS exposure looks like in a typical American.

Methods:
A finger-prick was used to draw capillary blood. The first drop of blood was wiped away with a PFAS-free gauze and the Mitra device is applied to the subsequent drops of blood. The four Mitra tips contained approximately 30 µL of blood and were stored at -20°C until extraction. Absorptive Mitra tips were then removed from the stem and placed in polypropylene vials with isotopically labelled internal standards or IDAs (Isotope Dilution Analytes) and acetonitrile to aid with protein removal. The samples are sonicated and allowed to equilibrate prior to a centrifuge step to condense the precipitated protein for easier removal. The supernatant was removed and the original tube with Mitra was washed with solvent and the centrifuge step repeated to ensure that PFAS were not absorbed to the vial. The extracts were then combined and solid phase extraction (SPE) was performed. Injection internal standards (ISs, or recovery standards) were added to the SPE extract immediately prior to placing it in a new polypropylene vial for analysis.

These extracts were injected onto a C18 column at 30°C. A secondary column was introduced as a delay column to counteract endogenous interferences from environmental PFAS compounds present in the system. Data were collected using a SCIEX QTRAP 7500 system using electrospray ionization (ESI) in negative mode. The Scheduled MRM Algorithm was used to optimize data sampling across each peak and maximize the dwell times used.

Results:
The assay showed excellent analytical reproducibility, precision, accuracy, and linearity. The total amount of PFOA detected was 0.82 ng/mL, however, only the linear version of perfluorooctanoic acid (PFOA) was detected. This value was slightly lower than the median value of 0.9 ng/mL for Americans aged 18-49 according to the United States Environmental Protection Agency. The total amount of perfluorooctanesulfonic acid (PFOS) detected was 1.862 ng/mL, which again is lower than the median value listed by the EPA of 2.6 ng/mL. Finally, perfluorohexanesulfonic acid (PFHxS) was detected at a value of 1.558 ng/mL or 2.7 times higher than the listed median EPA value of 0.6 ng/mL.

Conclusions:
A robust and sensitive workflow for the detection of PFAS in blood samples using the SCIEX QTRAP 7500 system was successfully developed. This low-level sampling approach means that at-home testing of these compounds is possible and can help the population understand their PFAS exposure and the implications PFAS may have on their own health. While the concentrations of PFOA and PFOS presented in this study remained under national median values, the high concentration of PFHxS likely was related to past exposure to aqueous film-forming foam (AFFF).