Low-level analysis of per-and polyfluoroalkyl substances (PFAS) requires high sensitivity and low background levels throughout the entire workflow from sample collection, transportation, and storage to analytical instrumentation and sample preparation. Resprep polymeric WAX SPE cartridges allow for accurate low-level quantitation of PFAS compounds in drinking water while meeting the requirements of EPA Method 533.<\/p>\n\n\n\n
Due to the low levels required by many regulatory agencies, the analysis of PFAS in drinking water often employs solid phase extraction (SPE) coupled with LC-MS\/MS to reach low detection limits. EPA Method 533 [1] uses weak anion exchange (WAX) SPE to better retain short-chain acid compounds and obtain part-per-trillion (ppt) detection limits. However, due to the ubiquitous nature of PFAS compounds, the selection and screening of all materials and consumables that contact samples, including SPE cartridges, is critical for maintaining a clean background and allowing continued low-level analysis. In this assessment, Resprep WAX cartridges were used with a Resprep QR-12 vacuum manifold to extract samples for EPA Method 533 PFAS analysis using a Shimadzu Nexera LC and 8045 MS\/MS. <\/p>\n\n\n\n
Spikes and blanks were prepared in polypropylene bottles using 250 mL deionized water spiked with isotope dilution standards as per EPA Method 533, Section 7.16.1. The 6 mL SPE cartridges, which contained 500 mg of 30 \u00b5m WAX (cat.# 28291*), were placed on a Resprep QR-12 vacuum manifold (cat.# 28298-VM) that was fitted with quick-replace liners (cat.# 28310-VM). Resprep sample delivery system lines (cat.# 26250) were used to transfer the samples to the SPE cartridges. While both the quick-replace liners and sample delivery lines contain PTFE, which can be a potential source of PFAS contamination, investigation of blanks taken using all lines and all ports on the manifold showed no detectable PFAS leaching. Thorough and regular blank checking of all SPE components and solvents, especially when using new lots of materials, is recommended to ensure that background contamination is below acceptable levels.<\/p>\n\n\n\n
After preparation of the samples and setup of the SPE system, the samples were extracted following the instructions in EPA Method 533, Section 11.4, which is summarized in Figure 1.<\/p>\n\n\n