Benchtop Matrix Assisted Laser Desorption Ionization Mass Spectrometry of PFAS for preliminary screening of environmental samples

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly persistent contaminants with adverse health and environmental impacts. Routine analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) can suffer from carryover and instrument contamination when samples contain elevated PFAS levels. A rapid, low-cost prescreening method helps identify high-concentration samples and minimize downtime and cleanup efforts.

Objectives and Study Overview

This study demonstrates a simple benchtop MALDI-TOF mass spectrometry workflow for preliminary PFAS screening in aqueous samples. The goal is to detect samples exceeding a chosen cutoff (100 ng/mL) before they enter the main LC-MS/MS pipeline.

Applied Methodology and Instrumentation

Samples and standards of PFOA, PFOS, PFHxA and PFBS were diluted in water. An internal standard (^13C8-PFOS) was spiked into PFOS samples. Two MALDI matrices (norharmane and TMGN) were tested. Final sample prep involved mixing 200 µL of sample with internal standard and matrix (TMGN at 5 mg/mL in 70% acetonitrile), then spotting 1 µL on FlexiMass-SR48 or FlexiFocus-96 slides. A Shimadzu MALDI-8030 instrument operated in negative mode (m/z 100–1000, 980 shots at 200 Hz) collected spectra. IMAGEREVEAL MS software produced whole-slide images.

Main Results and Discussion

TMGN provided more uniform spot homogeneity than norharmane. Limits of detection were established at 5 ppb for PFOA, 250 ppt for PFOS, 200 ppt for PFHxA and 1 ppb for PFBS. MALDI-MS imaging revealed PFAS migration to spot edges, guiding the use of annular acquisition for improved signal-to-noise. Whole-slide imaging of 48 spots was completed in ~12 minutes. Samples above the 100 ng/mL threshold displayed bright green in the intensity-coded images, enabling rapid visual discrimination of problematic samples in bottled water tests.

Advantages and Practical Applications

• Minimal sample preparation: single-step mixing with matrix and internal standard.
• Fast throughput: full slide analysis in under 15 minutes.
• Cost-effective entry-level instrumentation.
• Visual flagging of high PFAS levels to prevent LC-MS/MS contamination.

Future Trends and Opportunities

Expanding the method to a broader range of PFAS analytes and incorporating multiple internal standards could enable semi-quantitative screening. Automation of slide preparation and integration with laboratory information management systems (LIMS) would support high-throughput environmental monitoring. Further development may adapt the workflow to other classes of emerging contaminants.

Conclusion

The benchtop MALDI-TOF approach offers a simple and rapid prescreening tool for PFAS in aqueous samples, reducing risk of LC-MS/MS contamination and associated downtime. Confirmatory analysis by LC-MS/MS remains necessary for definitive quantification and regulatory compliance.

Used Instrumentation

• Shimadzu MALDI-8030 linear TOF mass spectrometer
• FlexiMass-SR48 and FlexiFocus-96 MALDI target slides
• IMAGEREVEAL MS imaging software

References

1. Shimadzu Application News LCMS-151.