Page 46 - Application Notebook - PFAS Analysis

No. SSI-LCMS-121

Liquid Chromatography Mass Spectrometry

Analysis of Per- and Polyfluoroalkyl

Substances (PFAS) Specified in EPA M533

No. LCMS-121 Using the Triple Quadrupole LC-MS/MS

■ Introduction
EPA published a new method for testing short chain Four replicates were prepared at each concentration
per- and polyfluoroalkyl substances (PFAS) in level and a minimum of four laboratory reagent
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drinking water. Method 533 measures PFAS by blanks (LRB) were also included in the extraction
isotope dilution anion exchange solid phase batches.
extraction and liquid chromatography/tandem mass
spectrometry (LC-MS/MS). The lowest concentration ■ Instrumental Method
minimum reporting levels (LCMRLs) for the method The analysis of 25 PFAS compounds, with16 isotope
analytes range from 1.4 to 16 ng/L. Shimadzu dilution analogues and 3 post extraction internal
Scientific Instruments was one of eight laboratories standards was performed using a UHPLC system
that participated in providing EPA with outside coupled with a triple quadrupole mass
laboratory validation data along with a review of the spectrometer. MRM transitions were optimized
method draft. This document summarizes Shimadzu using Flow Injection Analysis for all compounds .
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Scientific Instruments data from the validation study. Source parameters were optimized to reduce
fragmentation and increase sensitivity. Fluorotelomer
■ Analytical Method acids, observed as [M-H]- and [M-HF-H]- can result
Sample Preparation in an ion with the same m/z as the unsaturated
Solid Phase Extraction (SPE) with a WAX sorbent fluorotelomer acid. Even under optimized
(500 mg) was used for the extraction, as outlined in chromatography, these compounds have near
EPA method 533 (section 6.8.1). Each cartridge was identical retention times. The lower ESI heater
cleaned and conditioned first, following EPA 533 temperature reduces HF loss and minimizes false
(section 11.4.1). A vacuum manifold with a high- identification of fluorotelomer acids. The
volume sampling kit outfitted with large bore PEEK chromatographic parameters are based on the
tubing was used to reduce potential contamination. chromatographic method used in EPA Method 533.
A Shim-pack XR-ODS 50 x 3.0 mm column was used
All sample bottles were rinsed with the elution as a delay column, and a Phenomenex Gemini™
solvent prior to use. Each water sample (250 mL) C18, 2.0 mm ID × 50 mm, 3.0 μm particle size
was adjusted to pH 6-8 and fortified with PFAS column was used as the analytical column.
analyte and isotope dilution analogues, mixed, and Quantitation was performed using MRM on tandem
loaded onto the conditioned cartridge. Compounds mass spectrometer (LC-MS/MS). Figure 1 shows the
were eluted at a high pH from the solid phase with LCMS system used for this work (LCMS-8045);
two 5 mL aliquots of methanol containing 2% instrumental conditions are included in Table 1 and
ammonium hydroxide (v/v) and evaporated to retention times, MRM transitions and collision
dryness using nitrogen. Extracted samples were energies are listed in Table 2.
reconstituted to a final volume of 1 mL in 80:20
methanol:H2O with internal standards added.

Extraction for Precision & Accuracy study was
performed by fortifying five replicates of reagent
water and tap water samples at 10 ng/L. For LCMRL
calculations (results not shown here) samples were Figure 1: LCMS-8045 triple quadrupole mass spectrometer
extracted at eight concentration levels ranging from
0.2 ppt and 14 ppt.