Alpha Analytical now offers PFAS analysis of drinking water by 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.
This new PFAS analytical method was released by EPA in December 2019 and it includes some significant improvements over the existing EPA PFAS drinking water procedure, Method 537.1.
Comparison of Method 533 to 537.1
There are two primary procedural differences between the methods. Method 533 incorporates the use of extracted internal standards as part of an isotopic dilution quantification approach whereas Method EPA Method 537.1 does not. The use of the isotope dilution technique reduces the overall uncertainty associated with the analysis. Method 533 also uses a weak anion exchange (WAX) solid phase extraction (SPE) cartridge instead of the polystyrene divinylbenzene (SDVB) used in Method 537.1.
The use of the WAX SPE cartridge in Method 533 allows for additional PFAS compounds to be determined, particularly short chain PFAS not amenable to Method 537.1 analysis.
Expanded List of PFAS compounds
Method 533 lists 25 PFAS compounds that can be analyzed by the method and Method 537.1 lists 18 PFAS compounds. It should be noted that not all 18 of the Method 537.1 compounds can be determined by Method 533, even though it has a 25 compound list. The Method 533 list contains 14 Method 537.1 compounds, plus 7 additional compounds that are on DoD and other compound lists, as well as 4 totally new PFAS compounds that were previously not on any PFAS analytical list. Therefore, the maximum number of PFAS compounds that drinking water can be analyzed for using EPA compliance methods is 29 by using both Methods 537.1 and 533 to analyze the sample.
Holding Times and Preservatives
Another significant difference between the two methods are the holding times required by each. Method 533 allows for 28 days to extraction and 28 days to analyze whereas Method 537.1 only allows 14 days to extraction and 28 days to analyze. There are different preservatives used as well, ammonium acetate is used for Method 533 and Trisma is used with Method 537.1.
The table published on our website lists the two EPA drinking water target compounds as well as the Alpha proprietary isotope dilution and Total Oxidizable Precursors (TOP) PFAS target compound lists.