CEM - The Extraction of PFAS Molecules from Spiked Soil

Per- and polyfluoroalkyl substances (PFAS) are a group of manufactured chemicals that are used in a wide variety of industries because of their resistance to stains, grease, and high temperatures. They possess a chain of linked carbon atoms with fluorine atoms branching off the main chain. The presence of the strong carbon-fluorine bond contributes to the stability of these compounds, earning them the nickname “forever chemicals.” PFAS are used in products such as nonstick cookware, firefighting foam, and stain-resistant carpets.

Because of their persistent nature and their widespread use, this group of substances has leached into the environment with limited methods of remediation. Furthermore, these compounds have been found to bioaccumulate in animals and humans, and exposure in humans has been shown to cause adverse health outcomes, including cancer, infertility, and endocrine disruption. Thus, the assessment of the levels of PFAS in the environment is important to the health and safety of humans.

The EDGE, an automated solvent extraction system, was used to extract a subset of PFAS molecules from spiked soil samples. The EDGE was able to extract the soil samples in less than 10 min. The extraction yielded excellent recoveries and standard deviations. Furthermore, there was no carryover found between samples. The EDGE is an excellent choice for laboratories seeking to automate their PFAS extraction.

Method

Reagents

Clean sandy loam was purchased from MilliporeSigma. A PFAS standard containing 24 different compounds (Part number 99207) was purchased from Absolute Standards, Inc. HPLC-grade methanol, HPLC-grade water, HPLC-grade formic acid, and ammonium hydroxide were purchased from Fisher Scientific.

Sample Preparation and EDGE Method

Five grams of clean sandy loam was weighed directly into a Q-Cup® containing the S1 Q-Disc® stack (C9-G1-C9 sandwich). Each sample was spiked with 2 ng or 200 ng of standard in HPLC-grade methanol, resulting in low spike and high spike samples, respectively. Each set of spikes was done in triplicate. The sample was extracted with the EDGE using 80:20 methanol:water with 0.3% ammonium hydroxide using the method provided. Each set of spikes was extracted on the EDGE, and then a blank extraction of the system was done with a Q-Cup containing the S1 Q-Disc stack (C9-G1-C9 sandwich) to assess the level of carryover. Each extraction was collected in a polypropylene conical tube using an EDGE rack. The sample was brought up to a final volume of 20 mL using 80:20 methanol:water with 0.3% ammonium hydroxide, and 20 μL of formic acid was added to each sample to neutralize the sample. The samples were then analyzed by Pace Analytical.

EDGE Method

Q-Disc: S1 stack (C9-G1-C9 sandwich)
Extraction Solvent: 80:20 methanol:water with 0.3% ammonium hydroxide

Cycle 1

Top Add: 10 mL

Bottom Add: 0 mL

Rinse: 0 mL

Temperature: 65 °C

Hold Time: 3 min

Cycle 2

Top Add: 10 mL

Bottom Add: 0 mL

Rinse: 0 mL

Temperature: 65 °C

Hold Time: 4 min

Wash 1

Wash Solvent: Methanol Wash

Volume: 10 mL

Temperature: 50 °C

Hold: 3 s

Wash 2

Wash Solvent: 80:20 methanol:water with 0.3% ammonium hydroxide

Wash Volume: 10 mL

Temperature: None

Hold: None

Results

The recovery data in Table I, from the low and high spikes, indicated that the samples were extracted with high efficiency, with recoveries ranging from 63% to 101%. The resulting RSD values were also low, indicating the recovery data were reproducible. The extraction data from the empty Q-Cup indicated that there was no carryover of the spiked compounds within the system, indicating the wash was aggressive enough to remove any residual PFAS compounds.

Conclusion

The analytical assessment of PFAS compounds is critical because of their widespread nature, high stability, and adverse health effects. The EDGE was able to rapidly and efficiently extract spiked soil samples with excellent recoveries and RSD values. The EDGE also saw no carryover after extractions into the subsequent extraction. The EDGE is an excellent extraction tool for laboratories seeking to automate their PFAS extractions with great efficiency.

CEM Corporation

3100 Smith Farm Road, Matthews, NC 28104

tel. (800) 726-3331

Website: www.cem.com