PFAS are a class of highly stable synthetic organic compounds used in a wide variety of industrial and commercial applications. They are also highly stable in the environment and strongly bioaccumulate. As a result, they have become ubiquitous throughout the globe and are often referred to in today’s media as “Forever Chemicals“. Consequently, PFAS levels need to be tested in drinking water and more recently methods have been developed to measure PFAS in other environmental matrices that require more complex clean-up solutions, such as wastewater, soils, and sediments.

Accurate, Precise, and Economical PFAS Extraction Solution

The United States Department of Defense (DOD) is dealing with extensive PFAS contamination owing to the widespread use of PFAS-based Aqueous Film Forming Foam (AFFF) used as fire suppression foams at many military installations. As a result, DOD developed its own PFAS analytical guideline to help solve their installations’ unique environmental monitoring and clean-up challenges. The US EPA and DOD have been working jointly to validate EPA 1633 Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS. A single-lab validated draft method is the result of this collaboration method and calls for the use of a polymeric weak anion exchange (WAX) SPE sorbent in combination with graphitized carbon black (GCB) powder. For water samples, the process involves an initial SPE using a WAX cartridge followed by dGCB or the use of a second cartridge. For solid samples, dGCB is added to an initial ammonium hydroxide wash, followed by the WAX SPE cartridge.

Both methods add time, cost, and chances for increased errors to the clean-up procedure and present the opportunity for loss of analytes and introduction of imprecision.  

Strata PFAS SPE, wherein the two sorbents are contained within a single tube, offers the opportunity for decreased sample processing time and increased accuracy and precision. Strata PFAS is a stacked single cartridge solution with polymeric WAX and GCB sorbents that functions as a traditional Solid Phase Extraction (SPE) cartridge with a built-in polishing step. When comparing different recoveries for a small subset of analytes for a WAX SPE and dSPE GCB method versus Strata PFAS, the recovery is greatly improved using Strata PFAS. The results are shown in Table 1.

A routine Laboratory Control Sample (LCS) was conducted by a commercial testing laboratory highly experienced with PFAS analysis. The LCS had been spiked with all 32 target analytes at 25 μg/L and was analyzed with a batch of field samples to demonstrate method performance and data acceptability. As shown in Table 2, all 32 analytes were well within method recovery limits with an average recovery of 98.8% and a mean recovery of 99.0%, thereby demonstrating acceptability of the use of Strata PFAS in the performance DOD QSM5.1/5.3 as well as draft EPA 1633.

SPE Conditions for Analyte Extraction Using Strata PFAS SPE

Cartridge: Strata PFAS 200 mg WAX/50 mg GCB/ 6 mL)
Part No.:
CS0-9207
Condition 1:
4 mL 0.3 % Ammonium hydroxide
Condition 2:
4 mL Methanol
Equilibrate:
5 mL Water
Load:
Add sample at 4 mL/min
Wash:
2x 4 mL Water
Elute:
2x 4 mL 0.3 % Ammonium hydroxide in
Evaporate:
Methanol to dryness and reconstitute to 1 mL with Methanol/Water (96:4)

Table 1: Recovery Comparisons of WAX SPE and dSPE using GCB vs Strata® PFAS Single Cartridge Method

Analyte WAX SPE + dSPE GCB
% Recovery
Strata PFAS Stacked Cartridge
% Recovery
13C2-PFDoDA 77 84.5
13C2-PFTeDA 62 84.0

PFODA 38 78.3
PFHxDA 63 89.3

Table 2: Recovery of QSM 5.3 Target Analytes from a Laboratory Control Sample Using Strata PFAS SPE (WAX/GCB)

Analyte Actual
Concentration
Sample
Result
% Recovery Method Recommendation
Limits
Pass/Fail
PFBA 25.600 22.640 88 84-135 Pass
PFPeA 25.600 22.157 87 75-138 Pass
PFBS 22.640 22.300 99 81-133 Pass
4:2-FTS 23.920 22.078 92 64-134 Pass
PFHxA 25.600 24.644 96 80-137 Pass
PFPeS 24.000 21.699 90 82-132 Pass
HFPODA 25.600 26.336 103 70-130 Pass
PFHpA 25.600 27.018 106 80-140 Pass
PFHxS 24.200 24.713 102 71-131 Pass
DONA 24.120 26.083 108 70-130 Pass
6:2-FTS 24.280 24.217 100 51-155 Pass
PFHpS 24.360 23.015 94 80-129 Pass
PFOA 25.600 25.043 98 83-138 Pass
PFOS 24.480 22.492 92 54-139 Pass
PFNA 25.600 25.872 101 73-140 Pass
9Cl-PF3ONS 23.840 21.863 92 70-130 Pass
PFNS 24.560 21.993 90 71-121 Pass
PFDA 25.600 25.047 98 78-137 Pass
8:2-FTS 24.520 22.231 91 62-133 Pass
PFOSA 25.600 25.714 100 73-121 Pass
NMEFOSAA 25.600 30.906 121 53-136 Pass
PFDS 24.640 22.873 93 69-124 Pass
PFUnDA 25.600 26.353 103 70-134 Pass
NEtFOSAA 25.600 28.765 112 59-145 Pass
11Cl-PF3OUdS 24.120 22.625 94 70-130 Pass
PFDoDA 25.600 27.710 108 75-139 Pass
10:2-FTS 24.680 26.626 108 50-124 Pass
PFDoS 24.800 21.509 87 39-121 Pass
PFTrDA 25.600 25.814 101 67-144 Pass
PFTeDA 25.600 25.446 99 79-134 Pass
PFHxDA 25.600 29.662 116 36-136 Pass
PFODA 25.600 27.373 107 10-124 Pass

Andrew Patterson1 , Charles Neslund2 , Robert Brown2 , Sam Lodge3 , David Kennedy3 , and Brian Marshall3

1 Eurofins Environment Testing America, 800 Riverside Pkwy, Sacramento, CA, 95605, USA 2 Eurofins Environment Testing America, 2425 New Holland Pike, Lancaster, PA 17601, USA 3 Phenomenex, Inc., 411 Madrid Ave., Torrance, CA 90501, USA

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