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PFASs: Structure to Analysis - Why Analytical Chemistry is Critical March 16, 2017 EPAZ Gatekeeper Regulatory Roundup David A. Gratson, CEAC
PFASs: Structure to Analysis - Why Analytical Chemistry is CriticalMarch 16, 2017 EPAZGatekeeper Regulatory Roundup
David A. Gratson, CEAC
Discussion Topics/Outline
PFAS Structures Analytical Methods Chromatography Methods Non-chromatography Methods
PFAS Data Quality
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Per/Polyfluoroalkyl Substances (PFAS) Carbon “backbone” – the alkyl in PFAS All or several Cs substituted with F End Group(s) – polar +, - and zwitter ions :
Carboxylates
Sulfonates
Alcohols
PFAS Structures
PFCs
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Sulfonamide (positive charge)
Thioamide Sulfonates Sulfonamide Amino Carboxylates ( + & -) Betaines
PFAS Structures Continued
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Fluorotelomers (telomerization)
Nomenclature:
8:2 FtS
C (w/ F):C (w/out F)
PFAS Structures Continued
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~6,000 compounds
Wang, et al., ES&T, 2/2017
Electrochemical Fluorination (Historic) Mix of branched and linear isomers
Telomerization (Current) “Isomerically pure” product, retains starting material linearity DuPont 2002 major manufacturing process Major product C8 or C9
Some chain length impurities
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Formulations
Data to date indicate that microbes derive no energy from C-F bond breakage. Hence, natural degradation is not facilitated
Also do not hydrolyze, photolyze under environmental conditions 1 ( Nature: Scientific Reports May 2016 Tian et al.)
Require ~1200ºC for destruction Considered both hydrophobic and lipophobic (unlike Cl) Low polarizability* BCFs, Kow inconsistent with human elimination – total/speciation
required.
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Environmental Chemistry
* RT, environmental transport ∫ of polarizability -model
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8:2 Fluorotelomer Sulfonate (8:2 FtS)
PFOA (C8)
Reactive bonds
Precursor Degradation
Matrix Drinking Water Soil/Sediment: no published* methods Biota: no EPA/DOE published* methods
Serum/plasma: method CDC/Intercal/RIVO/AMAP (NHANES 2013)
Air: no published* methods Extraction Approach SPE for water Solvent extraction with solids
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* Agency/Normative reference and multi-laboratory validated
Chromatographic Methods
Published Methods US EPA Method 537.1 (Rev 1.1, Sept. 2009) Drinking Water Method, UCRM3 Method 14 Compounds Acceptable and non-acceptable modifications
DoD QSM (Ver 5.1, 2017?) ASTM D7979-15, ASTM D7968-14 ISO 25101, aqueous (2009)
Typical Detection Limits Water: 2 ng/L Soil/Sediment: 1µg/Kg Tissue: 0.25 µg/Kg
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LC/MS-MS
14 Analytes, all perfluoro Some method flexibility (MODs), but fairly specific Three labeled surrogates added, SPE extraction with MeOH Three labeled ISs added
LS –> MS –> CAD (MRM)–> MS
CAD: Not prescribed except 499 –>80 for PFOS
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Method 537.1
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LC/MS and LC/MS/MS
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CAD/MRM
DOES NOT ALWAYS
537.1 DoD QSM 5.1Allowed modifications specified If Modify, must clearly identify in SOP
even if method allowsDrinking water Multiple matricesCalibration Not force through originContainer set at 250 mL Range, default to QAPPSpiking/Dilutions Typical Multiple serial dilutions, spiking at all
reported dilutions
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Comparison of LC/MS/MS Methods
Contamination Purity and Availability of Standards Efficiency of Extraction beyond drinking water Matrix/Method interferences Rinsing of sample container (C8 retained) Aromatics MS cross talk (not selective, double charged)
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LC/MS/MS Issues
PFOS anion (C8F17O3S) 89 possible structural isomers, 11 known isomers, co-elute. How quantify individual/total? If > 1 peak – all peaks to be integrated. Reported as …?
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LC/MS-MS Branched/Linear LC Issues
Kärrman, et al., EnvironmentalChemistry 8(4) 372-380 2011 http://dx.doi.org/10.1071/EN10145
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Branch isomer is about 8% of the total area in this example
LC/MS/MS IssuesBranched and Linear ExampleBranched and Linear Example
Ionization Response Factorlinear ≠ Response Factorbranched
Yet don’t have standards for all isomers
CAD Issues Parent -> daughter 99 versus 80, different bias
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Riddell, N. et. al, Environ Sci. Technol. 2009 (43) 7902-7908
MS Issues
Each laboratory’s MOD is different and there are many mods! # of analytes, # surrogates, # ISs QC Criteria (Calibration, LCS, MS) Isotopically labeled IS/Surrogates CAD transition used for quantification
AFFFs that are percentage levels vs 70 ng/L. Dynamic range across PFASs (PFOA vs telomers) Currently, available analytical methods only examine a small fraction of
the potential compounds present (12-27 compounds).
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Issues
19F NMR (Moody et al. 2001, Arsenault et al. 2005). Combustion Ion Chromatography (Miyake, et al. 2007) TOP (Houtz, 2013 ES&T) LC/MS/MS http://www.envstd.com/top-analysis-more-to-consider-when-
monitoring-polyfluorinated-alkylated-substances/
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LC/MS/MS Low Bias?
Total Oxidizable Precursors (TOP): Goal is to completely oxidize polyfluorinated precursors Aqueous sample/extract 60 mM persulfate/0.125 M NaOH, 85°C
for 6 hours Reduce analytes/precursors to more stable/toxic Must not overwhelm oxidant Different product ratios noted (Houtz, ES&T 2012),incomplete
reaction Oxidation of 13C labeled PFOS (ALS Canada)
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Non-Chromatographic Methods
Particle-Induced Gamma-ray Emission (PIGE, Graham Peaslee, University of Notre Dame)
Aqueous matrix problem, must extract. PIGE vs NAA – 99.9% (total F) TOP vs PIGE – 30-100%.
LC/MS/MS <10% of total?
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LC/MS/MS Low Bias?
Union College
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... why not? US EPA-approved method is for
Drinking Water… MODIFIED METHODS!! - Data
Comparability!
Why Validate PFAS Data?
Issues from above Dynamic Range and Serial Dilution of Samples Calibration models Curves forced through 0 or not (EPA/DoD) Weighted (e.g. 1/x2)or not Isotopic Dilution
MDLs/LOD and positive results Signal-to-noise relative to average noise
Qualitative Identification
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Why Validate PFAS Data?
NFGs
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Validation Pre-Steps …(How)
Real chemists thinking real chemistry thoughts (not
geologists or engineers trying to be chemists)
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Validation Pre-Steps … (How)
Due to modified methods, you must first understand the laboratory’s approach. Obtain the SOPs and review and thoroughly understand them Audit the laboratory and their procedures, if necessary Prepare a Data Validation SOP that corresponds to the laboratory
data generation procedures and QC limits Internal standard quantitation & Isotopic dilution Extraction procedure for GW & solid samples Mixed branched and linear standards
Determine if they can prepare Level IV report Enjoy the ride
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Validation
IT’S THE WILD, WILD WEST OUT THERE!
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David Gratson, [email protected]
505-660-8521
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Environmental Standards, Inc.“Setting the Standards for Innovative Environmental Solutions”
Headquarters 1140 Valley Forge Road | PO Box 810 | Valley Forge, PA 19482 | 610.935.5577Virginia 1412 Sachem Place | Charlottesville, VA 22901 | 434.293.4039
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David Gratson Introduction
David is a Senior Technical Chemist, with Environmental Standards Inc. and works out of the Santa Fe, New Mexico office. He has over 30 years of applied and R&D environmental chemistry experience . Through his career he has provided analytical chemistry and regulatory expertise to private industry clients throughout the US, as well as the U.S. EPA, the Department of Energy, and NASA. He provides project and program level consulting and quality assurance oversight support for site investigations, permitting, and regulatory compliance.
Credentials/Bio
Fifteen years of consulting experience with Environmental Standards Inc and Neptune and Company.
Fifteen years of bench-level analytical chemistry experience including the National Renewable Energy Laboratory, NASA White Sands Test Facility, and Rocky Mountain Analytical Laboratories (now TestAmerica Denver).
Mr. Gratson holds an M.S. in Environmental Science and Engineering from the Colorado School of Mines and a B.S. from Allegheny College.
Please view his LinkedIn profile here:
https://www.linkedin.com/in/davidgratson
