Delay Columns: Additional Impacts to Delaying PFAS Present in the Background

Collaborative Efforts to Improve Environmental Monitoring
Oral Presentation

Presented by R. Marfil-Vega
Prepared by O. Shrestha, K. Luo, M. Davis, L. Wiest, E. Wang, R. Marfil-Vega
Shimadzu Scientific Instruments, 7102 Riverwood Drive, Columbia, MD, 21046, United States


Contact Information: [email protected]; 410-910-0884

ABSTRACT

There are significant method standardization efforts by organizations, such as EPA, FDA, ASTM, and AOAC for quantifying PFAS in various matrices. Several approaches are commonly used (e.g. installation of delay column, eliminate fluoropolymer-based tubing…) to minimize the presence of PFAS from LC-MS/MS instruments, that ultimately impact the achievable method detection limits on a routine basis. This work focused on the systematic evaluation of different delay columns and their overall potential impact on method performance for an accurate and sensitive PFAS analysis. Optimized multiple reaction monitoring of 40 PFAS, those included in EPA method 1633, along with 31 isotopically labelled PFAS compounds, were chromatographically separated using a C18 column (50x2.1 mm, 3 μm) and analyzed on a Shimadzu LCMS-8060NX triple quadrupole mass spectrometer. Three different C18 delay columns (A, B, C) with various lengths and diameters were incorporated between the mixer and autosampler through stainless steel tubing to investigate their impact on chromatography, target signal intensity, and their capability to reduce interferences from background PFAS. Data were collected and analyzed with and without the presence of delay columns. Targeted PFAS were observed during null (e.g. no vial) injections when a delay column was not installed. PFBA, PFPeA, PFNA and PFHxA, displayed substantial peak areas, contributing to false positive identifications in the standards and samples. As expected, upon installing a delay column, the PFAS present in system and mobile phase were effectively separated from the spiked compounds; however, the retention time shift varied with compound and delay column. Similarly, the peak area also changed (i.e. NEtFOSE: 2.5-fold increase between delay columns C and B, 1.8-fold increase between delay columns B and A). In this presentation we will compare the detailed performance of different delay columns and discuss their suitability to ensure adherence to evolving analytical demands included in various standardized methods.