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PFAS Analysis: What to Expect and How to Evaluate the Data

November 8, 2019

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Methods and Analyte Lists

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PFAS MethodsMethod Year Applicable Matrices # PFAS Analytes

EPA 537 v 1.1 2009 Drinking Water 14 analytes

EPA 537.1 2018 Drinking Water 18 analytes

ASTM D7979-17 2017 Water, Wastewater 21 analytes

ASTM D7968-17 2017 Soil 21 analytes

ISO 25101 2009 Aqueous PFOA/PFOS

DoD QSM 5.1 2017 Solid & Aqueous 24+ analytes

DoD QSM 5.2 2018 Solid & Aqueous 24+ analytes

EPA 537 “Modified” Current All 24+ analytes

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Current PFAS Reportable by Analytical LaboratoriesAnaly te CAS No. UCMR3

(6)537(14)

NYSDEC(21)

ISO 25101(2)

MDEQ IPP(24)

Perfluorobutanoic acid (PFBA) 375-22-4 X XPerfluoropentanoic acid (PFPeA) 2706-90-3 X XPerfluorohexanoic acid (PFHxA) 307-24-4 X X XPerfluoroheptanoic acid (PFHpA) 375-85-9 X X X XPerfluorooctanoic acid (PFOA) 335-67-1 X X X X XPerfluorononanoic acid (PFNA) 375-95-1 X X X XPerfluorodecanoic acid (PFDA) 335-76-2 X X XPerfluoroundecanoic acid (PFUnA) 2058-94-8 X X XPerfluorododecanoic acid (PFDoA) 307-55-1 X X XPerfluorotridecanoic Acid (PFTrA) 72629-94-8 X X XPerfluorotetradecanoic acid (PFTeA) 376-06-7 X X XPerfluorohexadecanoic acid (PFHxDA) 67905-19-5Perfluorooctadecanoic acid (PFODA) 16517-11-6Perfluorobutanesulfonic acid (PFBS) 375-73-5 X X X XPerfluoropentanesulfonic acid (PFPeS) 2706-91-4 XPerfluorohexanesulfonic acid (PFHxS) 355-46-4 X X X XPerfluoroheptanesulfonic Acid (PFHpS) 375-92-8 X XPerfluorooctanesulfonic acid (PFOS) 1763-23-1 X X X X XPerfluorononanesulfonic acid (PFNS) 474511-07-4 XPerfluorodecanesulfonic acid (PFDS) 335-77-3 X XPerfluorooctane Sulfonamide (FOSA) 754-91-6 X XN-methyl perfluorooctane sulfonamidoacetic acid (NMeFOSAA) 2355-31-9 X X XN-ethyl perfluorooctane sulfonamidoacetic acid (NEtFOSAA) 2991-50-6 X X X6:2 Fluorotelomer sulfonic acid (6:2 FTSA) 27619-97-2 X X8:2 Fluorotelomer sulfonic acid (8:2 FTSA) 39108-34-4 X X4:2 Fluorotelomer sulfonic acid (4:2 FTSA) 757124-72-4 X10:2 Fluorotelomer sulfonic acid (10:2 FTSA) 120226-60-0N-Methyl perfluorooctane sulfonamidoethanol (N-MeFOSE) 24448-09-7N-Ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) 1691-99-2N-Methyl perfluorooctane sulfonamide (MeFOSA) 31506-32-8N-Ethyl perfluorooctane sulfonamide (EtFOSA) 4151-50-2HFPO-DA (Gen-X) 62037-80-3 XADONA XF-53B-9Cl XF-53B-11Cl X

Analyte lists vary by method, laboratory, and regulatory agency

Determine what list you really need!

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“Modified” EPA 537

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Typical sample result summary form

Number of PFAS reported

Results, RLs, units

Dilution results

Collection date, prepared date, analysis date

Percent solids (dry weight)

Isotope Dilution recoveries

Evaluate Holding Times14 days to extraction; 28 days from extraction to analysis

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Is the lab extracting the entire sample and rinsing the sample bottle? What cartridge is the lab using?

– Styrenedivinylbenzene (SDVB) sorbent phase– Reverse phase copolymer characterized by a weak anion exchange (WAX)

sorbent phase Is the lab doing washes to remove interferences on the SPE cartridge?

Solid Phase Extraction

250 mL sample 1 mL final extract

PFBA, PFPeA poor recoveries

DoD 5.1 vs 5.2

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Separates compound mixtures on column. Column has high affinity for PFAS. The affinity of each compound to the column is different based on its solubility.

Characteristic retention times

Step 1 in compound identification: time the compound comes off the column

Sample Analysis: HPLC Separation (Part 1)

Retention time increases with carbon number

Analyte Retention Time (min)

PFBA 1.52713C4PFBA 1.525

PFOS 3.02813C4PFOS 3.026

Retention time

DoD 5.1 vs 5.2

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Unique fragmentation patterns (Step 2 of compound identification ) Parent/daughter combinations = definitive ID, more sensitive analysis

Sample Analysis: MS/MS (Part 2)

Analyte Retention Time (min) Parent/Daughter Ions

PFBS 1.754 299/80299/99

13C3PFBS 1.752 302/83

PFOS 3.028 499/80499/99

13C4PFOS 3.026 503/809

Definitive Identification of Compounds– Retention time from HPLC separation– Transition to characteristic daughter ions– Ion ratios

What happens when the ion ratios are outside limits?– What are the limits?

What if there is no daughter/confirmation ion?– PFBA– PFPeA– NMeFOSAA– NEtFOSAA

Transition Ions (Parent/Daughter Ions)

Analyte Retention Time (min)

Parent/Daughter Ions

Ion Ratio

Ion Ratio Limit

PFBS 1.754 299/80299/99 2.91 1.35-

4.0513C3PFBS 1.752 302/83 NA NA

PFOS 3.028 499/80499/99 4.19 2.04-

6.1213C4PFOS 3.026 503/80 NA NA

DoD 5.1 vs 5.2

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Before September 2016, some inconsistency in how this performed PFHxS, PFOS, PFOA, NMeFOSAA, NEtFOSAA If branched isomers not included, result is biased low.

Linear & Branched Isomers

Correct integration of PFOA Incorrect integration of PFOA

Retention Time

Parent/daughter ions

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Sample spiked with KNOWN amount of isotopes (labeled surrogates or extracted internal standards)

Isotopes match target analytes

– 13C4PFBA is isotope associated with PFBA

– 13C4PFOS is isotope associated with PFOS

– etc. for each PFAS analyte

Target PFAS result corrected by proportional amount based on isotope

BENEFITS:

– Corrects for analytical error associated with matrix

– Corrects for matrix interferences

Isotope Dilution: What is It?

Concentration Target PFAS = Target PFAS Area * True Concentration IsotopeArea Isotope * Calibration Factor

EPA 537 and ASTM Method do NOT utilize isotope

dilution

DoD QSM requires isotope dilution

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When is the lab spiking the isotopic standards? How is the lab evaluating the recoveries of the isotopic standards?

If >10% recovery, results most likely not significantly affected. If <10% recovery, higher probability that results may be affected.

– Some data validation guidelines recommend rejecting nondetect results if <10%.

– Detected results: potential low bias– Only associated target PFAS affected

How Can Isotope Dilution Vary Between Labs?

Surrogate Lab 1 (%) Lab 2 (%) Lab 3 (%) Lab 4 (%) DoD (%)13C3-PFBS 25-150 50-150 26-148 31-159 50-150

13C3-PFHxS 25-150 50-150 34-126 47-153 50-15013C4-PFHpA 25-150 50-150 35-126 30-139 50-15013C8-PFOA 25-150 50-150 43-112 36-149 50-15013C8-PFOS 25-150 50-150 43-115 42-146 50-15013C9-PFNA 25-150 50-150 32-134 34-146 50-150

Example:If 13C3-PFBS exhibits low %R, only affects PFBS.

DoD 5.1 vs 5.2

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When samples are diluted Example: Sample contains 2000 ng/L PFOS. Isotope spiked in at 50 ng/L.

Requires a 50-fold dilution– Isotope standard now diluted out. – How will result be quantified if no recoverable isotope standard?

Lab performs dilution and then adds more of the isotope spike to the extract just prior to analysis.– Recovery of isotope 90-100%– Final result not accounting for matrix effects

If sample also analyzed undiluted or less-diluted– Recovery of isotope 50-60%– Use this recovery to correct result from diluted analysis

Correcting concentration of analyte for 90-100% versus 50-60% will result in a low-biased value

Is Isotope Dilution Ever a Problem?

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Typical sample result summary form

Number of PFAS reported

Results, RLs, units

Dilution results

Collection date, prepared date, analysis date

Percent solids (dry weight)

Isotope Dilution recoveries

PFAS Analytical Reports

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Purposes:Method Blank: To check for potential lab contamination in the sample preparation and analysis step

Field/Equipment Blanks: To check for potential contamination from ambient field conditions or equipment

Does each prep batch have its own method blank?

Blanks: Method Blanks, Field Blanks, & Equipment Blanks

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Is anything detected in the blank?

Are there any potential false positives?

General Rule of Thumb: If concentration in sample <2x the blank concentration, the result is potentially a false positive

Blank Evaluation

2x Blank = 4 ng/L

Sample conc = 7 ng/L

Real Hit

2x Blank = 4 ng/L

Sample conc = 3 ng/L

False Positive

PFOS in Blank = 2 ng/L

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Laboratory Control Samples (LCS)

• Purposes: To check the accuracy of the method in the absence of any matrix effects

• What are LCSs?

• Does each analytical or prep batch have its own LCS?

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Were all target analytes reported?

Were all recoveries within the acceptance limits?

If LCS recoveries are outside limits:– POTENTIAL LOW BIAS or– POTENTIAL HIGH BIAS

Affects the whole batch of samples prepared with the LCS.Potentially unusable results:

– if recoveries are <10%

LCS Evaluation

ACCURACY

DoD 5.1 vs 5.2

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Matrix Spikes/Matrix Spike Duplicates (MS/MSDs)

What are these? Were these analyses performed on a project sample?

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MS/MSD

• Were all target analytes reported?• Were all recoveries within the acceptance limits?

• Were all RPDs within the acceptance limits?

• If MS recoveries are outside limits:– POTENTIAL LOW BIAS or– POTENTIAL HIGH BIAS

Affects the sample that was spiked.

Potentially unusable results: – if recoveries are <10%

ACCURACY

PRECISIONDoD 5.1 vs 5.2

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Let’s Summarize Potential Biases

• Detected results Blanks

• Missed holding timesHolding Times

• Low recoveries• High recoveriesLCS

• Low recoveries• High recoveries

Labeled Surrogates, Matrix Spikes

Subsampling Water Sample

No Methanol Rinse on Bottle

HIGH BIAS

LOW BIAS

LOW BIAS HIGH BIAS

LOW BIAS HIGH BIAS

All Associated Samples in Batch}Sample-Specific}

All Associated Samples in Batch}

Sample-Specific}

LOW BIAS >C8 PFSAs & >C10 PFCAs: Sample-Specific}

LOW BIAS Long chain PFAAs : Sample-Specific}

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Detection Limits

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Different Detection Limits

Detection Limit Accurate? Precise?

Use to Demonstrate

Below Cleanup Standards?

Use Valuesin Risk

Assessment?

IDL No Yes No No

EDL1 No Yes Yes Yes

MDL / DL No Yes No No

LOD2 No Yes Yes Yes

PQL Yes Yes No No

RL / QL / SQL / LOQ Yes Yes Yes Yes1Specific to dioxins/furans2Specific to DoD projects 24

RLs most reliable value (aka LOQ, QL, SQL, ML, CRQL) Most labs RLs 2-10 ng/L, depending on PFAS Do not use MDLs as nondetect values No J values

What To Use for PFAS?

PFBA: 0.35 J ng/L PFBA: <2.0 ng/L PFBA: 2.5 ng/L25

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Typical sample result summary form

Number of PFAS reported

Results, RLs, units

Dilution results

Collection date, prepared date, analysis date

Percent solids (dry weight)

Isotope Dilution recoveries

PFAS Analytical Reports

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CAS Numbers and PFAS State

PFAS State Structure CAS No.

PFOAAnion Perfluorooctanoate C7F15CO2

- 45285-51-6

Acid Perfluorooctanoic acid C7F15COOH 335-67-1

PFOSAnion Perfluorooctane sulfonate C8F17SO3

- 45298-90-6

Acid Perfluorooctane sulfonic acid C8F17SO3H 1763-23-1

Labs should report acid form and CAS No. for acid

DoD 5.1 vs 5.2

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Standardized Methods in the Future?

Future Method Matrix Calibration Analytes/RLs When?

SW-846 8327 Aqueous(non-DW)

Direct injection; External standard

24 PFAS;RL 10 ng/L

Out for public comment soon

SW-846 8328 Aqueous and solids Isotope dilution

24 PFAS in 8327 plus Gen-X; RL 10 ng/L

Spring 2019; EPA

collaborating with DoD

SW-846 8329 Solid prep method NA NA Not definite

New Drinking Water Method Drinking Water SPE; Internal

standardShorter chain

PFASJune 2019; EPA ORD &

Office of Water

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Summary – Take Away Points

No standard PFAS Analytical Method for non-DW matrix

SOPs are inconsistent across laboratories

Differences between DoD QSM 5.1 and 5.2

Evaluate the reported QC results

Understand what your lab’s procedures are

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Questions?Elizabeth Denly, ASQ CMQ/OEP: (978) 656-3577 | E: EDenly@TRCCompanies.comwww.TRCcompanies.com