Ultimate Sensitivity for the Detection of Per- and Polyfluorinated Alkyl Substances in Environmental Water Samples

Polyfluoroalkyl Substances (PFAS) in the Environment (Session 2)
Oral Presentation

Prepared by K. Organtini, K. Rosnack, D. Stevens, S. Oehrle, F. Dorman
Waters Corporation, 34 Maple St, Milford, MA, 01757, United States


Contact Information: [email protected]; 508-482-3242

ABSTRACT

Sensitivity limits are constantly being challenged with the continued evolution in regulations and guidelines for per- and polyfluorinated alkyl substances (PFAS). It is still unknown what the official regulations from the US EPA will become, but if they follow similar guidance to the European Drinking Water Directive, individual PFAS could be regulated around 1 ng/L (parts per trillion). Direct injection approaches have become popular for PFAS analysis since they reduce the sample preparation time, and more importantly limit the risk of introducing contamination. Generally, this approach requires large injection volumes of 30 µL or more. With the introduction of the enhanced sensitivity of a new tandem quadrupole, large volume injections are no longer necessary to reach the required sensitivity in the ng/L range.

To be successful with a direct injection approach for PFAS analysis, instrument sensitivity is extremely important. Initial evaluation was performed using solvent standards to understand instrument sensitivity. Peak area, peak height, and signal to noise were used to make this evaluation. Enhancements were experienced in all three parameters, indicating a true sensitivity increase without a detriment to signal to noise. Previous applications of the direct injection approach required a 30 µL injection volume, but with the increased sensitivity, injection volume was reduced to 10 µL. Even using the reduced injection volume, limit of detection (LOD), determined using a S:N of 3, for most compounds was near or below 1 ng/L.

Preliminary work in water matrix focused on drinking water samples. The addition of matrix did not significantly impact sensitivity. Several carboxylates and sulfonates were detected in drinking water in the single digit ng/L range using only a 10 µL injection. Further work will demonstrate sensitivity in other types of water samples using the direct injection approach.