Direct Probe Ionisation Mass Spectrometry for Rapid and Accurate Determination of Perfluoroalkyl and Polyfluoroalkyl Substance Concentrations

Abstract

Rationale

Analysis of perfluoroalkyl and polyfluoroalkyl substances (PFAS) is typically achieved using chromatographic techniques, such as high-performance liquid chromatography, combined with mass spectrometry. These techniques can be complex, expensive, time consuming and can lead to inaccurate quantification due to sample container sorption and contamination by polytetrafluoroethylene (PTFE) components.

Methods

Here, we demonstrate the novel application of a Direct Probe ionisation Mass Spectrometer (DPiMS) to quantify four aqueous anionic PFAS; perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA) and 1H,1H,2H,2H-perfluorooctanesulfonic acid (6:2 fluorotelomer surfactant). The DPiMS was operated in both Single Ion Monitoring (SIM) and broad m/z scan range (50–500) modes and the cleaning methodology, ionising voltage and desolvation line heating temperature were optimised.

Results

The derived method quantified both single component and mixtures of PFAS from 0.5 nM to 200 μM (0.2 ppb to 108 ppm) without use of pre-concentration. The advantages of this technique over chromatographic techniques are; the speed of analysis (≈3.5 min per sample, including blanks/cleaning), lack of PTFE components and simplified methodology.

Conclusions

The DPiMS is a useful tool for the rapid screening and estimation of PFAS concentrations with results that are comparable to existing methods. It is anticipated that better sensitivity could be achieved with the use of a triple quadrupole instrument.