Orbitrap GC and LC Workflows for Non-targeted Analysis Using Dispersive Liquid-liquid Microextraction (DiLLME) Sample Preparation

Per- and Polyfluoroalkyl Substances (PFAS) in the Environment
Oral Presentation

Presented by E. George
Prepared by C. Grim1, V. Thibert2, A. Ganci3, B. Gauriat3, J. Garnier4
1 - Thermo Fisher Scientific, 355 River Oaks Pkwy, San Jose, CA, 95134, United States
2 - Thermo Fisher Scientific, 16 avenue du Québec, , BP30210, 91941, France
3 - Thermo Fisher Scientific, 16 avenue du Québec, Courtaboeuf Cedex, BP30210, 91941, France
4 - Thermo Fisher Scientific, 16 avenue du Québec, Courtaboeuf Cedex, BP30210, 919, France


Contact Information: [email protected]; 408-300-4267

ABSTRACT

Per- and polyfluorinated alkyl substances (PFAS) are a class of bioaccumulative, often toxic small molecules featured in environmental targeted methods, including EPA 533 and 537.1. However, these labor-intensive solid phase extraction (SPE) methods require 250 mL of water and only measure a handful of the thousands of known PFAS compounds due to a lack of standard availability and compatibility with SPE sorbents. This work describes an automated dispersive liquid-liquid microextraction (DLLME) method applied to water samples to reduce solvent consumption, cost-per-sample, and sample contamination. These extracts were analyzed using a targeted quantitative and non-targeted screening LC-Orbitrap MS method. Non-targeted results were compared against a 40,000+ PFAS compound library including a new in silico predicted transformation library.

A panel of 53 PFAS compounds of interest to both North American and European regulatory bodies was quantified alongside untargeted analysis across multiple environmental matrices. Quantitative results show limits of quantitation down to part per trillion levels for most analytes from an initial volume of only 15 mL of sample. The automated DLLME method provides a cleaner, more concentrated sample than direct injection approaches while providing some of the sensitivity gains seen from solid phase extraction. PFAS are present in many common lab supplies such as pipette tips and gloves, meaning removing manual steps also reduces the probability of sample contamination.

By using an orbitrap mass analyzer, high mass accuracy reduces chances of false formula assignments. With the new in-silico library, more tentative candidate structures with empirical formulas could be determined. Reviewing putative library identifications alongside other factors such as retention time correlated with mass, molecular mass divided by number of carbon atoms, and mass defect provides a multifaceted approach to identifying PFAS compounds. This overall workflow provides an automated solution to both quantify known PFAS and explore unknown PFAS with confidence.