LC-MS Analysis of PFAS Compounds

Petra Lewits, Product Manager Analytical Chromatography, HPLC Columns, Cory Muraco, Product Manager, Liquid Chromatography Technology

Merck

Article from Analytix Reporter - Issue 13

Introduction

PFAS (Per- and poly-fluoroalkyl substances) are persistent, man-made organic compounds, widely found in the environment. Recent awareness has brought attention to the toxicity of these substances. The U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) have initiated actions against PFAS. For determination of PFASs, liquid chromatography–mass spectrometry (LC-MS) is a commonly used technique.

The EPA has developed, validated, and published three methods to support the analysis of 29 PFAS in drinking water, method 533, 537 and 537.1. EPA 8327 covers the analysis of selected per- and polyfluoroalkyl substances (PFAS) in prepared extracts of various matrices (e.g., waters and solids) by liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis.

The Ascentis^® Express PFAS HPLC column is designed for the separation of novel and legacy short-chain and long-chain PFAS compounds containing branched and linear isomers, whilst adhering to EPA methodology requirements.

Furthermore, a specific PFAS delay column prevents background PFAS contamination from interfering with the sample results in quantitative LC-MS methods (Figure 1).

Figure 1. LC-MS instrumental set-up for PFAS analysis & results of perfluorooctanoic acid (PFOA) (MRM 413.0>368.0) using a delay column

The selectivity data for the different EPA method compounds under the conditions outlined in Table 1 is displayed in Figure 2-4 and Table 2.

Figure 2. PFAS analysis with Ascentis^® Express PFAS column and PFAS Delay column under EPA Method 533 conditions (Peak IDs in Table 2)

Figure 3. PFAS analysis with Ascentis^® Express PFAS column and PFAS Delay column under EPA Method 537.1 conditions (Peak IDs in Table 2)

Figure 4. PFAS analysis with Ascentis^® Express PFAS column and PFAS Delay column under EPA Method 8327 conditions (Peak IDs in Table 2)

Table 1. LC-MS Conditions

LC Conditions
Analytical column:	Ascentis® Express PFAS, 100 x 2.1 mm I.D., 2.7 μm (53559-U)
Delay column:	Ascentis® Express PFAS Delay, 50 x 3 mm I.D., 2.7 μm (53572-U)
Mobile phase:	[A] 10 mM Ammonium acetate;  [B] methanol
Gradient:	Time	% B
	0.0	33.0
	18.0	98.0
	18.1	100.0
	21.0	100.0
	21.1	33.0
	26.0	End
Flow rate:	0.4 mL/min
Injection volume:	2.0 µL
Pressure:	485 bar
Temperature:	35 °C
Sample solvent:	Methanol (96%), water (4%)
MS Conditions
Detection:	ESI(-) MS/MS
LC system:	Shimadzu Nexera X2
ESI LCMS system:	Shimadzu LCMS-8040
Spray voltage:	-2.0 kV
Nebulizing gas:	2 L/min
Drying gas:	15 L/min
DL temp:	250 ˚C

Table 2. MS transition and retention data

		EPA 533		EPA 537.1		EPA 8327
Compound	Transition	Peak #	tR (min)	Peak #	tR (min)	Peak #	tR (min)
PFBA	213.0000>169.0000	1	1.36			1	1.36
4:2FTS	229.0000>85.0000	2	1.89			2	1.89
PFPeA	263.0000>219.0000	3	3.22			3	3.22
PFBS	299.0000>80.0000	4	3.81	1	3.789	4	3.81
PFHpS	279.0000>85.0000	5	3.97			5	3.97
PFPeS	315.0000>135.0000	6	4.79			6	4.79
PFMPA	327.0000>307.0000	7	5.43
PFHxA	313.0000>269.0000	8	5.68	2	5.639	7	5.68
PFEESA	349.0000>80.0000	9	6.10
HFPO-DA	285.0000>169.0000	10	6.34	3	6.307
PFHpA	363.0000>319.0000	11	7.76	4	7.723	8	7.76
PFHxS	399.0000>80.0000	12	7.99	5	7.936	9	7.99
ADONA	377.0000>250.9000	13	8.01	6	7.978
FOSA	427.0000>407.0000					10	9.30
PFOA	413.0000>369.0000	14	9.40	7	9.368	11	9.40
PFMBA	449.0000>80.0000	15	9.51
PFDS	295.0000>201.0000					12	9.70
PFNA	463.0000>419.0000	16	10.75	8	10.715	13	10.75
PFOS	499.0000>80.0000	17	10.79	9	10.762	14	10.79
9Cl-PF3ONS	530.9000>351.0000	18	11.46	10	11.439
PFNS	527.0000>507.0000					15	11.84
PFDA	513.0000>469.0000	19	11.89	11	11.857	16	11.89
8:2FTS	549.0000>80.0000	20	11.90			17	11.90
N-MeFOSAA	570.0000>419.0000			12	12.336	18	12.37
6:2FTS	498.0000>78.0000	21	12.68			19	12.68
NFDHA	599.0000>80.0000	22	12.85
PFUnA	563.0000>519.0000	23	12.86	13	12.822	20	12.86
N-EtFOSAA	584.0000>419.0000			14	12.827	21	12.87
11Cl-PF3OUdS	630.7000>451.0000	24	13.33	15	13.311
PFDoA	613.0000>569.0000	25	13.71	16	13.690	22	13.71
PFTrDA	663.0000>619.0000			17	14.435	23	14.45
PFTeDA	713.0000>669.0000			18	15.083	24	15.10

Learn more about PFAS analysis at SigmaAldrich.com/PFAS

1. EPA Method 533: Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry. [Internet]. Available from: https://www.epa.gov/dwanalyticalmethods/method-533-determination-and-polyfluoroalkyl-substances-drinking-water-isotope

2. EPA 537.1 Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). [Internet]. Available from: https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10111J4.txt

3. EPA Method 8327 Per-and Polyfluoroalkyl Substances (PFAS) by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). [Internet]. Available from: https://www.epa.gov/hw-sw846/sw-846-test-method-8327-and-polyfluoroalkyl-substances-pfas-liquid-chromatographytandem