:true:
The Power of Precision
false
us
ZenoTOF 7600 system
X500R system
X500B system
View all
SelexION device
SCIEX 7500 system
SCIEX Triple Quad 6500+ system
SCIEX 5500+ system
QTRAP 6500+ system
QTRAP 4500 system
Citrine system
4500MD system
Jasper system
View all mass spectrometers
Intabio ZT system
Echo MS system
Biologics Quant solution
Biotransform solution
MPX 2.0 High Throughput Multiplexing system
View all integrated solutions
BioPhase 8800 system
CESI 8000 Plus system
PA 800 Plus system
P/ACE MDQ Plus system
GenomeLab GeXP system
View all capillary electrophoresis
Advance your research with front-end instruments designed to help you realize the full power of your mass spectrometer. SCIEX has the broadest portfolio of ESI-MS front-ends that can facilitate various flow rates, sample requirements and sensitivities. No one else offers the entire range of analytical flow, microflow, nanoflow LC-MS and even ultra-low flow CESI-MS.
ExionLC 2.0 series
Micro HPLC columns
M5 MicroLC system
View All
Ultra-low Flow CESI-MS
View all front-end HPLC MS
Differential mobility spectrometry (DMS) and ion mobility spectrometry are analytical techniques used to separate ions based on their gas phase mobility. Multiple types of ion mobility devices exist, such as drift tubes, traveling wave, and high-field asymmetric waveform devices. Learn how you can separate yourself with Differential Ion Mobility.
The latest ion sources from SCIEX enable enhanced sensitivity and robustness with greater desolvation range across all MS platforms, from Triple Quad to QTRAP and QTOF.
Turbo V ion source
OptiFlow Turbo V ion source
OptiFlow Interface
View all ion sources
vMethod applications are pre-configured and verified LC-MS/MS methods that reduce the need for method development – significantly cutting the time, effort and money to deploy a new assay. Every vMethod provides method conditions, recommended sample prep, LC and MS conditions, and details for applicable MS/MS library databases for key applications.
AA45/20 1.0
aTRAQ
Illicit drugs
Acrylamide
Allergens
Antiobiotics/veterinary drugs
Cannabinoids
Illegal dyes
Melamine
Mycotoxins
Pesticides
Industrial chemicals (bisphenol)
Industrial chemicals (ethanolamines)
Pesticides (herbicides)
Pesticides (Polar)
Pharmaceutical and personal care products (PPCPs)
Peptide and protein bioanalysis
Routine biologics characterization
Benzodiazepines
Blood screening
Drugs of abuse
Etg and ets
Nicotine
THC-COOH
Urine screening
Explore vMethod applications
Software downloads
Software activation
Software support policy
Software support plans
Software feature request portal
Software partners
SCIEX OS software
Biologics Explorer software
Cliquid software
DiscoveryQuant software
Molecule Profiler software
OneOmics suite
View all software
High resolution and QTRAP libraries can dramatically enhance the quality of your analysis, giving you much improved confidence in your data. With a comprehensive library at your fingertips, you can easily create methods and process targeted and non-targeted screening data on your complex samples, faster and easier than ever before.
All in one library
SCIEX all-in-one HR-MS/MS library with NIST 2017
Antiobiotic Llbrary
Flurochemical library
Forensic library
Mycotoxin library
Natural products
Pesticide library
Wiley Libraries
Antibiotic library
Meta library
Explore the library selector tool
Boost the performance of your mass spectrometer and improve sensitivity, productivity, and data precision. iChemistry Solutions are the world's only reagents and consumables that are custom designed with your success in mind.
RNA 9000 Purity & Integrity kit
aTRAQ kit for amino acid analysis of hydrolysates
aTRAQ kit for amino acid analysis of physiological fluids
Protein CE-SDS Purity Analysis kit
MS calibration kits
CZE rapid charge variant analysis kit
BioPhase Fast Glycan Labeling and Analysis kit
iTRAQ reagent
mTRAQ reagent
View all consumables
QTOF – Quadrupole Time of Flight
QTRAP® – Triple Quad Linear Ion Trap
SWATH® – Data Independent Acquisition
SelexION® – Differential Mobility Separation
MicroLC – Microflow Chromatography
Ultra Low-Flow CESI-MS Technology
iCIEF-MS Technology
Nominal Mass LC-MS-MS
Acoustic Ejection Mass Spectrometry
View All Technology
ADME and DMPK
Biomarker quantitation
Cell therapy
CRISPR/Cas9 analysis
Viral vector characterization
Biomarker discovery
High-throughput mass spectrometry
Metabolite identification
Targeted protein degraders and PROTACs
Extractables and leachables
Pharma impurities
Residual nucleic acid analysis
Lipid nanoparticles and non-viral carrier
Messenger RNA analysis
Plasmid and DNA analysis
Synthetic oligonucleotide analysis
ADC analysis
Cell line analysis
Charge heterogeneity analysis
Glycan analysis
Intact protein analysis
Multi-attribute methodology
Peptide mapping analysis
Subunit mass analysis and middle-down
View all Biopharma and pharma
Clinical research
Clinical diagnostics
Clinical Mass Spec Operators
Clinical Method Developers
Clinical Lab Managers
View All Clinical
PFAS
Pesticides & herbicides
PPCP
Disinfection by-products
Soil and biota
Ethanolamine
Synthetic polymers
Exposome
Suspect screening
Nanomaterials
View All Environmental Testing
How do you protect your reputation and meet today’s global food safety standards? Whether you are a commercial lab or a food manufacturer, the quality of your food testing data is vital to your business. SCIEX solutions help you meet maximum residue limits (MRLs) with high-quality data that you can genuinely count upon. With a portfolio of applications, your lab can quickly and easily react to diverse market needs.
Pesticide Testing
Mycotoxins Testing
Antibiotics Testing
Potency Testing
Mycotoxin Testing
Terpenes Profiling
Meat Speciation Testing
Food Fraud Analysis
Food Adulterant Testing
Food Dye Testing
Food Omics
Allergen Testing
Ingredient Authenticity & Profiling Analysis
Packaging & Food Contact Substance Analysis
View All Food and Beverage Testing
How do you ensure the integrity of your results in an industry that is never constant? By accurately detecting even the smallest compound angles you can deliver evidence that stands. SCIEX forensic analysis solutions deliver fast, highly accurate data across a multitude of compounds and biomarkers, from the known to the new and novel.
Forensic toxicology
Homeland security (coming soon!)
Cannabis and hemp potency testing
Doping control
View All Forensic Testing
Discovery Proteomics
Next-Generation Proteomics
Targeted Proteomics
Untargeted Lipidomics
Targeted Lipidomics
Untargeted Metabolomics
Targeted Metabolomics
Metabolic Flux Analysis
Gene Expression Analysis
DNA Sequencing
Genotyping and SNP Analysis
STR Analysis
AFLPs
View All Life Science Research
The SCIEX Now Learning Hub offers the most diverse and flexible learning options available, with best-inclass content that helps you to get the most out of your instrument and take your lab to the next level. Available personalized learning paths based on the latest memory science ensure better knowledge retention, and automated onboarding and enrollment means you’ll get up and running faster.
SCIEX Now Learning Hub offers the most diverse and flexible learning options available, with best-in-class content that helps you to get the most out of your instrument and take your lab to the next level. Available personalized learning paths based on the latest memory science ensure better knowledge retention, and automated onboarding and enrollment means you’ll get up and running faster.
SCIEX Learning Manager provides you with the infrastructure to assign, monitor and report on your staff's competency through a single digital platform. Effectively manage the training process for new hires, ensure continuous staff development and access information with a single log-in to your SCIEX account.
You can browse, filter, or search our extensive list of training offerings. Choose from over 100 self-paced eLearnings or search for an instructor-led course near you. Once you select the course you want to take, you will be directed to Learning Hub for enrollment (login required).
Login to SCIEX Now Learning Hub
Success Programs at Your Site
Online Course Catalog
Clinical Knowledge Center
Application Scientist Training at Your Site
China
Europe
German CE Courses
India
Japan
Korea
North America
UK
Visit all Training
Support cases
SCIEX Now Learning Hub
Instruments
Manage my instruments
Registered software
Activate software
Resource library
My notifications
Request support
Course catalog
SCIEX Store
SCIEX Now New Feature Request
Visit your SCIEX Now™ Dashboard
Declaration of conformance
Safety data sheets
Certificates of analysis
View All regulatory documents
Customer documents
Software and IT services
Compliance services
Lab optimization
Customized training
Relocation services
LC-MS service plans
Protect Plus Suite for your new LC-MS
CE service plans
Clinical service plans
StatusScope remote monitoring
Software accelerator program
Premium access content
Academic partnership program
Academic partners
View all partnership programs
Join the SCIEX community today to interact with your peers, share and exchange ideas, develop your knowledge, stay up-to-date with the latest products, post insights and questions, comment on others and receive support. This community is designed to help you, our customers, move science forward and get the answers you need. We’re committed to engaging with and listening to you, to create the best customer experience possible and to contribute to the success of your work.
Biopharma
Clinical
Environmental / Industrial
Food and Beverage
Forensics
Life Science Research
Pharma
Technology
Knowledge Base Articles
Course Catalog
Software Downloads
Request Support
SCIEX Now Feature Requests
Software Feature Requests
Newsletter Archive
Featured Content
FAQs
View All Community
About SCIEX
About Danaher
Customer Profiles
Echo® MS Center Of Excellence
Our History
Our favorite papers
Meet our executives
Career opportunities
Contact us
Press releases
In the news
Awards
Sustainability
You've got questions. We've got experts who can help. Contact us to find out more, talk to a specialist, explore our solutions or get expert support.
Talk to a specialist
Request more information
Request a quote
SCIEX success network
Frequently asked questions
SCIEX community
Request hosted catalog
Request punchout
Global public relations
508-782-9484
Country/Region Canada Mexico United States
Country/Region Argentina Brazil Chile Colombia Costa Rica Ecuador El Salvador Guatemala Peru Uruguay Venezuela
Country/Region Germany Albania Austria Belgium Bosnia and Herzegovina Bulgaria Croatia Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Ireland Italy Latvia Lithuania Luxembourg Macedonia Montenegro Netherlands Norway Poland Portugal Romania Serbia Slovakia Slovenia Spain Sweden Switzerland United Kingdom
Country/Region Bangladesh Brunei Darussalam Cambodia 中国 Hong Kong India Indonesia 日本 한국 Singapore Sri Lanka Taiwan Thailand Viet Nam
Country/Region Bahrain Iran Iraq Israel Jordan Kuwait Lebanon Oman Pakistan Palestine Qatar Saudi Arabia Syria Turkey United Arab Emirates Yemen
Country/Region Algeria Angola Botswana Burundi Egypt Ethiopia Kenya Liberia Libya Morocco Rwanda South Africa Tunisia Uganda United Republic of Tanzania Zambia Zimbabwe
Country/Region Armenia Azerbaijan Belarus Georgia Kazakhstan Kyrgyzstan Moldova Russia Tajikistan Turkmenistan Ukraine Uzbekistan
Country/Region Australia Micronesia New Zealand
AB Sciex is doing business as SCIEX. © 2010-2018 AB Sciex. The trademarks mentioned herein are the property of the AB Sciex Pte. Ltd. or their respective owners. AB SCIEX™ is being used under license. Beckman Coulter® is being used under license. Product(s) may not be available in all countries. For information on availability, please contact your local representative. For research use only. Not for use in diagnostic procedures.
Download tech note (PDF)
Simon Roberts1, KC Hyland1, Craig Butt1, Scott Krepich2, Eric Redman3, and Christopher Borton1 1SCIEX, USA; 2Phenomenex, USA; 3TestAmerica Laboratories, Sacramento, USA
This technical note describes two methods for the quantitation of per- and polyfluorinated alkyl substances (PFASs) in water samples. Both methods achieved accurate quantitation at levels of approximately 1-10 ng/L for more than 17 PFASs. Method 1 is compatibility with EPA Method 537.
PFASs are unique chemicals whose physicochemical properties make them important for use in a variety of industrial and consumer products including carpets, cookware, food packaging, fire suppressants, and others.1 Chemically, PFASs are aliphatic structures containing one or more C atoms on which H substituents have been replaced by F atoms. Classification and naming is typically by the particular functional group present, such as carboxylic acids, sulfonates, phosphonic acids, etc., as well as the length of the carbon chain. Desirable in various industrial applications for their chemical stability and low reactivity, these properties also make PFASs highly resistant to degradation in aquatic environments. Typical concentrations of PFASs found in various environmental water sources range from pg/L to µg/L levels.2
Human exposure to PFAS residues has been implicated in the incidence of cancer, obesity, endocrine system disruption, and other adverse health effects.3-4 In recognition of these potential risks, sources of human exposure to these chemicals (e.g., via drinking water) are receiving public and scientific attention.
PFASs exhibit relatively high aqueous solubility and can be transported and bioaccumulated from contaminated water sources. The US EPA maintains health advisory limits for select PFASs (e.g., perfluorooctanoic acid (PFOA) at a limit of 70 ng/L) in water, but these levels have been exceeded in some areas experiencing extreme point source inputs of these chemicals.5
Given the tremendous persistence of PFASs in the environment and their known presence in human populations exposed via drinking water and other environmental routes, demonstration of the capability for accurate and precise low-level quantitation is paramount for research and testing laboratories. Robust quantitative analytical methods utilize the specificity and sensitivity of LC-MS/MS with MRM monitoring. However, a primary analytical challenge to this assay is the prevention and reduction of background PFASs originating from the LC system and contamination during sample collection and preparation.
This application note presents two methods for the quantitation of per- and polyfluorinated alkyl substances (PFASs) in water samples. While the MS/MS detection method using the SCIEX Triple Quad™ 5500 System is similar between the two methods, the sample preparation and injection volume differ significantly.
Standards and internal standards (IS): The PFAS standards and internal standards were obtained from Wellington Laboratories (Guelph, Ontario) and were prepared in Baker HPLC-grade methanol. Standard stock solutions were prepared by dilution with 96% methanol and 4% water (purified using a Millipore water purification system).
Sampling and sample preparation: Water samples were obtained anonymously from various sources in the United States. Samples were stored in the dark at 4°C in 250 mL high density polyethlyene bottles until analysis.
Chromatography: Shimadzu LC-20ADXR binary pumps with a Shimadzu DGU-20A5 degasser was used for separations. All fluoroethylene polymer (FEP) tubing on the Shimadzu pumps and degasser was replaced with PEEK tubing with similar internal and external dimensions. A Phenomenex Luna C18(2) column (dimensions shown in Table 1) was installed between the pump mixing chamber and the column, outside of a Shimadzu CTO-20AC column oven. This column served as a delay or hold-up column to isolate PFAS contamination originating from the pumps and eluents. A longer and/or larger diameter Luna C18(2) column must be installed on heavily contaminated systems to prevent breakthrough of contamination.
Chromatographic separation was performed using a Phenomenex Gemini C18 HPLC column at 0.6 mL/min (Table 1). The Gemini C18 column was heated to 40°C in the column oven. A PAL-HTC-xt autosampler with dynamic load-wash (DLW) was modified by replacing all FEP tubing from the rinse solvent lines, the needle seal, and the sample holding loop with PEEK or stainless steel. The autosampler syringe and sample holding loop was rinsed with methanol and 1:1 methanol:acetonitrile between samples.
Table 1. LC columns for methods 1 and 2.
Method 1: Solid phase extraction and 10 µL injection: A mixture of surrogate standards (25 ng) was added to 250 mL water samples in the sampling bottle, and the entire volume was extracted using weak anion exchange SPE as recommended by ISO standard 251016. The empty sample container was rinsed with 10 mL of methanol with 0.3% NH4OH, which was then added to the SPE tube to elute the PFASs. The extract was evaporated to dryness, reconstituted in 500 µL of 80% methanol/20% water, and transferred to a polypropylene vial for analysis. All standards and blanks were also prepared at a final methanol concentration of 80%.
For Method 1, 10 µL injections of the standards and samples were analyzed using a 6.5 min gradient method (Table 2) with a 7.5 min total runtime, including the 1 min autosampler injection cycle. Water with 20 mM ammonium acetate was used as the “A” solvent and methanol was the “B” solvent.
Table 2. LC gradient for method 1 at a flow rate of 0.6 mL/min.
Method 2: Dilution and large volume injection: A 1 mL aliquot of a water sample was added to a 2 mL clear glass autosampler vial with a polyethylene septum cap containing 0.65 mL of methanol and a mix of surrogate standards at a final concentration of 50 ng/L. The final concentration of methanol in the diluted sample was 40%, and standards, blanks, and quality control samples were all prepared at the same concentration. A PAL HTC-xt autosampler was modified to inject 950 µL of the diluted samples and standards.
For Method 2, samples were analyzed using an extended 15.5 min gradient method (Table 3) with a 17.5 min total runtime, including the 2 min autosampler injection cycle. Water with 20 mM ammonium acetate was used as the “A” solvent, and methanol was the “B” solvent.
Table 3. LC gradient for method 2 at a Flow Rate of 0.6 mL/min.
MS/MS detection: A SCIEX Triple Quad 5500 System with a Turbo V™ Ion Source and ESI probe was used for analysis in negative polarity. The ion source parameters were optimized for the LC conditions using the Compound Optimization (FIA) function in Analyst® Software (Table 4).
One characteristic MRM transition was monitored for each analyte and internal standard (Download method information 8 ). The Scheduled MRM™ Algorithm was activated to monitor compounds only during a 60 second expected retention time window to maximize dwell times and optimize the cycle time of the method. As a result, all of the peaks in the calibration contained >12 points per peak.
Calibration was performed using a 7-point curve at concentrations of 25, 50, 250, 1000, 2500, 10000, and 20000 ng/L for Method 1 and 1, 2, 5, 20, 50, 100, and 200 ng/L for Method 2. Quantitation was performed using MultiQuant™ Software 3.0.2 using 1.0 Gaussian smoothing and 1/x2 weighted linear regression. PFASs with matched isotopically labelled surrogate standards were quantified using isotope dilution, while PFASs without matched surrogate standards were quantified using internal standard calibration with structurally similar isotopically labeled standards (full analyte and internal standard list shown in Appendix Figure 1). A concentration factor of 500 was applied to samples analyzed using Method 1, and a dilution factor of 1.65 was applied to samples analyzed using Method 2.
Table 4. Ion source parameters for methods 1 and 2.
The Gemini C18 column was selected for both methods based on its strong retention and predictable resolution of PFASs. All of the other columns tested exhibited breakthrough of the short chain acids in the column dead volume during optimization of the 950 µL injection method. The Luna C18(2) column was selected as the delay column for both methods after initial testing indicated that it provided better separation of PFAS contamination than other columns. For PFASs, blank contamination is a major concern for analysis due to potential contamination during sample preparation or contamination originating from analytical instrumentation. Figure 1 shows a small carryover peak at 2.5 min for PFHxS in a blank analyzed immediately following the injection of the highest calibration standard of 20,000 ng/L. The area of the carryover peak was only 0.078% of the highest standard and 21% of the lowest calibration standard for Method 1 (25 ng/L). The second peak at 3.2 min in Figure 1 is attributed to delayed PFHxS contamination originating from the HPLC pumps. Without the delay column, this contamination would instead focus on the analytical column and elute at 2.5 min along with the standard and sample peak.
A 50 mm x 2 mm, 3 µm Gemini C18 column was selected for Method 1, which utilized a 10 µL injection volume. The chromatographic separation of 25 PFASs is shown in Figure 2. The average peak asymmetry factor for the first 2 eluting peaks (PFBA and PFBS) in the initial calibration standards was calculated to be 1.3 in Method 1 using MultiQuant Software 3.0.2. This is within the acceptance criteria set by EPA 537 of 0.8-1.5 7.
Partial resolution of the branched and linear isotopes is necessary for PFAS analysis to distinguish between samples containing only linear isotopes or isotope mixtures. As shown in Figure 2, the earlier eluting branched isotopes are clearly distinguishable from the major peak corresponding to the linear isotopes for the 2 compounds that contained both branched and linear isotopes in the standards (PFHxS and PFOS). Most methods recommend that these two peaks are summed for quantitation, which was performed in this method using MultiQuant Software 3.0.2.
Figure 1. Evaluating carryover. Overlaid MRM traces for PFHxS in the lowest calibration standard (black, 25 ng/L) and a blank injection (blue) that followed the highest concentration standard (20 µg/L). The delayed peak in the calibration standard trace represents the ambient LC system contamination retained by the delay column.
Figure 2. Method 1 chromatography. Overlaid Chromatograms of a 1 µg/L Standard Injected using Method 1.
The initial 7-point calibration for Method 1 exhibited good accuracy within +/- 30% of the expected values for all points, accuracy within +/- 10% for the lowest calibrator, and R2 coefficients of >0.990, as shown in Table 5. Based on the S/N ratio of the low calibrator and the linearity of the curve, the calibration range could be extended on both the high and low levels to improve the dynamic range. A water sample analyzed using Method 1 exhibited concentrations of several PFASs ranging from 0.974 to 53.3 ng/L, as shown in Figure 3.
Figure 3. Overlaid chromatograms of PFASs quantified in a water sample using method 1. This method uses a solid-phase extraction and a 10 µL injection.
Method 2 is a large-volume, direct aqueous injection method designed for drinking, surface, and ground water samples. After the addition of surrogate standards and a simple dilution with methanol, 950 µL of the sample was injected directly onto the Gemini C18 column. In contrast to Method 1, a longer and larger diameter column was used to improve retention of the analytes in the large volume injection. This resulted in a longer total runtime (17.5 minutes compared with 7.5 minutes), but provided robust results for the large volume injection and minimal retention time shift (Figure 4). The only compound that exhibited deteriorated peak shape due to the large injection volume was PFBA. However, the broadened peak shape of PFBA did not affect quantitation accuracy or precision.
Similar to Method 1, blank contamination from the instrument was minimized by using a delay column in Method 2. Blank contamination from sample preparation was also minimized in Method 2 by reducing the number of pipetting steps and testing all new batches of solvents prior to use. The integrated areas of the first blank after the highest concentration sample (200 ng/L) were less than 50% of the lowest calibrator. For example, the area of the first blank analyzed after the 200 ng/L calibration standard was 22% of the area of the 1 ng/L standard for PFOA as shown in Figure 5. The other blanks shown in Figure 5 exhibited even lower response for PFOA, which could be contributed to laboratory contamination for the method blank and solvent contamination for the instrument blank.
Figure 4. Method 2 chromatography. Chromatogram of a 10 ng/L matrix spike into groundwater that was diluted with methanol and injected according to Method 2.
Figure 5. Overlaid PFOA traces for method 2. Overlaid traces in a 1 ng/L calibration standard and a series of blank injections analyzed using Method 2: a blank injection following a high concentration standard, a method blank, and an instrument blank analyzed before the calibration standards.
To be compatible with common sampling practices, the Method 2 was not optimized for recovery of the longest chain PFASs, PFHxDA and PFODA, from the sample container or from the autosampler vial. Due to the stronger hydrophobicity of these compounds compared with the shorter chain PFAS, PFHxDA and PFODA appeared to bind to polypropylene containers when the methanol concentration was <40%. Modifications to this method to improve the recovery and precision of PFHxDA and PFODA analysis may include collecting smaller samples (10-20 mL), diluting the entire sample with methanol in the sampling container, and adding surrogate standard directly to the sampling container.
Direct analysis of water samples is impaired by the presence of 5 g/L Trizma in samples, which is added to drinking water samples as a requirement by EPA method 537. Trizma suppresses ionization of the PFASs and elutes slowly from the column for minutes after the injection. Therefore, Trizma should not be added to samples that will be analyzed using direct aqueous injection, but is fully compatible with SPE as performed in Method 1.
Similar to Method 1, the initial calibration results for Method 2 exhibited good accuracy within +/- 30% of the expected values for all points, accuracy within +/- 10% for the lowest calibrator, and R2 coefficients >0.990, as shown in Table 5. In the development of Method 2, calibration standards for 6:2 and 8:2 FTS, MeFOSA, EtFOSA, MeFOSAA, and EtFOSAA were not analyzed in the full calibration curve.
Table 5. Calibration curves for method 1 and 2. Sensitivity and linearity from 25 to 20,000 ng/L and 1 to 200 ng/L (coefficient of regression, R2) using Method 1 and Method 2, respectively. S/N calculated using MultiQuant Software 3.0.2.
Because large-volume injection methods are less common for PFASs compared with offline extraction methods, this application note reports the recovery and precision of continuing calibration standards over 1 week of continuous water sample analysis to demonstrate the robustness and accuracy of Method 2. The chromatogram and quantitated values for several PFASs in one of these water samples are shown Figure 6.
As shown in Table 6, a continuing calibration standard at 20 ng/L analyzed 1 week after the initial calibration exhibited quantitative accuracy of 92-99% for all compounds with the exception of PFTrDA (81%) and PFBS (84%). Due to limited availability of surrogate standards, PFBS was analyzed using 18O2 PFHxS as an internal standard, and PFTrDA was analyzed using 13C2 PFDoA. The absence of an exact isotope-labelled surrogate for these two compounds likely contributed to the decreased accuracy of the ongoing calibration standard.
During the 1 week period of full-time water sample analysis, 9 replicates of the 20 ng/L continuing calibration verification (CCV) were analyzed as shown in Table 6. The precision (%CV) for all of the PFASs was <5%, which indicates excellent precision for the large volume injections. The surrogate recovery, calculated as the response of the surrogate standard in the 20 ng/L ongoing calibration standard divided by the response of the surrogate standard during the initial calibration, was within 73-120% for all of the PFASs analyzed.
Figure 6. Overlaid MRM traces of PFASs detected in a groundwater sample with the calculated concentrations of each PFAS. The sample was prepared and analyzed using Method 2.
Table 6. Method 2 accuracy. Accuracy of a 20 ng/L CCV analyzed 1 week after the initial calibration and precision of 9 replicates of a 20 ng/L CCV analyzed between 5 and 7 days after the initial calibration using Method 2.
The 2 methods reported here were designed for optimum robustness using the SCIEX Triple Quad 5500 System as the analytical platform. Both methods may be expanded to include soil, sediment, and biological extracts. Minimum and maximum reporting limits of approximately 1 ng/L to 400 µg/L could be achieved using both methods. These ranges could be expanded by increasing the extracted volume in Method 1 or by further dilutions in Method 2. The example chromatograms shown in this application note also demonstrate that the lower calibration levels than the levels analyzed here could be included in initial calibration curves to further improve the sensitivity of the method.
Method 1 has the advantage of compatibility with EPA Method 537 and allows sample concentration using solid phase extraction. Method 2 has the advantages of minimal sample preparation and fewer steps to introduce lab-based PFAS contamination. With the growing need for PFAS analysis of environmental samples, these versatile methods will be useful for labs aiming to evaluate growing lists of PFASs.
SCIEX acknowledges TestAmerica (Sacramento, CA) for collaborating with SCIEX by providing and conducting the analysis of standards for this application note. SCIEX also acknowledges Phenomenex (Torrence, CA) for providing HPLC columns and expertise for this application note and other method development efforts.