Evaluating Membrane Filters for Accurate PFAS Air Emission Analysis with OTM-45: Laboratory and Field Investigations

Air Monitoring, Methods, and Technology
Poster Presentation

Prepared by L. Lozeau1, R. Muralidharan2, M. Dube1
1 - MilliporeSigma, 400 Summit Drive, Burlington, MA, 01803, United States
2 - MilliporeSigma, 3050 Spruce Street, St. Louis, MO, 63178, United States


Contact Information: [email protected]; 781-496-5656

ABSTRACT

OTM-45 for analyzing perfluoroalkyl substances (PFAS) in emissions from stationary sources is a complex method that includes a sample collection train of seven stack gas fractions, the first of which is a heated membrane filter to collect the particulate phase. Two key considerations for any consumable used in a PFAS method are (1) to minimize contamination, and (2) to characterize baseline levels of analyte binding, as both can significantly impact result accuracy. This two-part study evaluated the suitability of glass fiber membrane filters (GFFs) for OTM-45 through both laboratory cleaning assessments and field pilot investigations. In the first part of the study, cleanliness was determined in the laboratory by exposing blank GFFs from different manufacturers, including Millipore® AP40 glass fiber, to the cleaning and front-half extraction sections of OTM-45. PFAS analytes were quantified in the extracts using C-13-labeled internal standards and LC-MS/MS. On a per-filter basis, no PFAS was detected above the reporting limit (RL). However, consistent levels of some perfluoroalkyl carboxylic and sulfonic acids (PFCAs/PFSAs) were estimated between the RL and method detection limit (MDL). The second part involved field sampling at two locations. Front-half sample collection was carried out at each site, followed by extraction and LC-MS/MS analysis of the extracts using internal standards. Analyte hits and recoveries were similar and consistent between membrane filters from different manufacturers, especially for PFCAs. Overall, recovery of C-13-labeled standards when sampled in the field versus those of blank GFFs from the cleanliness study were comparable. Certain compounds demonstrated consistently poor recoveries, especially fluorotelomer carboxylic acids, which may be due to uncertainty for these compounds in the method parameters. These data demonstrate that Millipore® AP40 glass fiber membrane filters are suitable for use in the sampling train for analyzing PFAS compounds in stationary sources by OTM-45.