Since its initial publication in 2020, EPA Method 533 has become a leading approved analytical test method for the analysis of PFAS in drinking water.  During this time, Merit Laboratories has analyzed thousands of samples utilizing EPA Method 533 for drinking water. 

In the publication of EPA Method 533 in 2020, Merit Laboratories was just a few national laboratories acknowledged in the approved method for PFAS testing in drinking water released by the U.S. EPA. Merit was acknowledged in the approved method for completing a validation study using EPA 533 and was recognized for providing valuable feedback on the method procedures and reviewing the draft method manuscript.

The U.S. EPA officially approved Merit Laboratories to perform analytical laboratory testing for PFAS compounds as part of the fifth Unregulated Contaminant Monitoring Rule (UCMR 5). As part of UCMR 5, Merit Laboratories is approved for analytical methods EPA 533 and EPA 537.1. UCMR 5 includes all 29 PFAS compounds that are within the scope of EPA Methods 533 and 537.1. Merit Laboratories is also NELAP accredited for EPA 533.

EPA 533 is a solid phase extraction (SPE) liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of select per- and polyfluoroalkyl substances (PFAS) in drinking water. Isotope dilution is incorporated into the method, which can minimize sample matrix interference and improve data quality. EPA 533 requires the use of MS/MS in Multiple Reaction Monitoring (MRM) mode to enhance selectivity. The method states that EPA 533 is intended for use by analysts skilled in the performance of solid phase extractions, the operation of LC-MS/MS instrumentation, and the interpretation of the associated data.

EPA 533 supports a variety of monitoring applications, which include the analysis of multiple short-chain per- and polyfluoroalkyl substances (PFAS) that cannot be measured by Method 537.1.  The release of Method 533 helped the EPA satisfy a commitment specified in the PFAS Action Plan to develop new validated methods to accurately test for additional PFAS in drinking water.

The analyte list identified in EPA Method 533 for laboratory testing in drinking water include:

• 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)

• 9-Chlorohexadecafluoro-3-oxanonane-1-sulfonic acd (9Cl-PF3ONS)

• 4,8-Dioxa-3H-perfluorononanoic acid (ADONA )

• Hexafluoropropylene oxide dimer acid (HFPO-DA)

• Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)

• Perfluorobutanoic acid (PFBA)

• Perfluorobutanesulfonic acid (PFBS)

• 1H,1H, 2H, 2H-Perfluorodecane sulfonic acid (8:2FTS)

• Perfluorodecanoic acid (PFDA)

• Perfluorododecanoic acid (PFDoA)

• Perfluoro(2-ethoxyethane)sulfonic acid (PFEESA)

• Perfluoroheptanesulfonic acid (PFHpS)

• Perfluoroheptanoic acid (PFHpA)

• 1H,1H, 2H, 2H-Perfluorohexane sulfonic acid (4:2FTS)

• Perfluorohexanesulfonic acid (PFHxS)

• Perfluorohexanoic acid (PFHxA)

• Perfluoro-3-methoxypropanoic acid (PFMPA)

• Perfluoro-4-methoxybutanoic acid (PFMBA)

• Perfluorononanoic acid (PFNA)

• 1H,1H, 2H, 2H-Perfluorooctane sulfonic acid (6:2FTS)

• Perfluorooctanesulfonic acid (PFOS)

• Perfluorooctanoic acid (PFOA)

• Perfluoropentanoic acid (PFPeA)

• Perfluoropentanesulfonic acid (PFPeS)

• Perfluoroundecanoic acid (PFUnA)

Merit Laboratories is a leading national PFAS environmental laboratory, analyzing drinking water, soil, wastewater, groundwater, and other sample matrices, including biosolids and sludge. Analytical methods performed by Merit for PFAS include drinking water by EPA 533, EPA 537.1, and EPA 537 rev. 1.1, biosolids by ASTM D7968-17 with Isotopic Dilution, and soil, wastewater, groundwater, and surface water by ASTM D7979-19 with Isotopic Dilution, ASTM D7968-17, and development of the new EPA 1633 method.