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An interlaboratory study on EPA methods 537.1 and 533 for per‐ and polyfluoroalkyl substance analyses

The US Environmental Protection Agency (EPA) Methods 537.1 and 533 were developed for analysis of per‐ and polyfluoroalkyl substances (PFAS) in drinking water. They have been also widely used for source water assessments. However, there are few studies reportedly supporting such applications. The main purpose of this interlaboratory study was to evaluate the performance of these two methods for use with both potable and nonpotable waters. The obtained matrix spike recoveries indicate that both methods are generally applicable for analysis of PFAS in pristine nonpotable water matrices, however, with a notable challenge for effectively extracting long‐chain PFAS from some nonpotable water matrices. Another challenge associated with EPA Method 533 is the impacts likely caused by co‐extracted common inorganic anions on those PFAS that do not have their own isotopically labeled analogues available. The experimental results indicate that these challenges can be successfully resolved or reduced by enhancing postextraction bottle rinsing and elution procedures.