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

Importance of the Topic

PFAS are persistent environmental contaminants with adverse effects on human health and sensitive analytical instruments. A rapid, simple screening method helps prevent instrument downtime and ensures safe sample workflows.

Objectives and Overview

This study develops a cost-effective MALDI-TOF MS prescreening protocol on an entry-level benchtop instrument to identify samples with high PFAS levels before they enter LC-MS/MS analysis.

Methodology and Instrumentation

PFAS standards (PFOA, PFOS, PFHxA, PFBS) were prepared from 1 ppm acetonitrile stocks and diluted in water. Samples were mixed 1:1 with 5 mg/mL TMGN in 70% acetonitrile, then 1 µL was spotted onto FlexiMass slides. Analysis used a MALDI-8030 with:

• Negative polarity
• Mass range m/z 100–1000
• 980 shots at 200 Hz
• 200 blanking
• 400 pulsed extraction

Main Results and Discussion

Detection limits: PFOA 5 ppb; PFOS 250 ppt; PFHxA 200 ppt; PFBS 1 ppb. TMGN matrix produced more homogeneous spots compared to norharmane. Whole-slide imaging of 48–96 spots completed in ~12 min allowed visual differentiation of high (>100 ng/mL) and low (<100 ng/mL) PFAS using red-green intensity mapping with a 100 ng/mL cutoff.

Benefits and Practical Applications

This protocol requires minimal preparation (200 µL sample), delivers rapid results (<15 min per slide), and flags potentially contaminated samples, reducing LC-MS/MS decontamination needs and improving laboratory throughput.

Future Trends and Opportunities

Implementing multiple internal standards could enable semi-quantitative analysis. Expanding the PFAS panel, automating slide handling, and enhancing imaging software will further optimize routine environmental monitoring workflows.

Conclusion

A benchtop MALDI-TOF MS prescreening method effectively identifies samples with elevated PFAS, serving as an efficient front-end tool to guide confirmatory LC-MS/MS testing.

References

1) Shimadzu Application News LCMS-151