Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Food Samples by LC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of synthetic fluorinated compounds widely used in industrial and consumer applications. Their exceptional chemical stability leads to persistence in the environment and accumulation in living organisms. Dietary intake through plant-based foods such as carrots is a significant exposure route, highlighting the need for robust analytical methods to monitor PFAS contamination.

Goals and Study Overview

The main objective was to develop and validate a rapid and reliable LC–MS/MS method for quantifying forty PFAS in frozen-ground carrot samples. Specific aims included optimizing extraction, clean-up procedures, and chromatographic separation to achieve high recovery rates and minimal matrix effects.

Methodology and Instrumentation

The sample preparation followed a QuEChERS-inspired protocol: 10 g of homogenized carrot was extracted with acetonitrile containing salts (MgSO4, NaCl, citrate buffers). Two weak anion-exchange SPE cartridges (InertSep MA-2 and EVOLUTE EXPRESS WAX) were compared. A sequential washing and elution strategy was established using methanol–water mixtures with formic acid or ammonia modifiers. LC–MS/MS analysis employed a Shim-pack Scepter C18 column with a 15-minute gradient (20→100% acetonitrile) and a triple-quadrupole mass spectrometer in ESI negative mode. A delay column prevented background contamination.

Used Instrumentation

• UHPLC: Shimadzu Nexera X3 with Shim-pack Scepter C18-120 column
• Mass spectrometer: Shimadzu LCMS-8050, ESI negative mode
• SPE cartridges: InertSep MA-2 (GL Sciences) and EVOLUTE EXPRESS WAX (Biotage)
• Auto-sampler vials: TORASTM-H Bio Vial

Main Results and Discussion

Optimized SPE conditions yielded recoveries between 70 and 120% for most PFAS with both cartridge types. Matrix effects were mitigated by reducing injection volume to 1 µL. A concentration step using nitrogen blow-down was found to cause significant losses for certain fluorotelomer carboxylic acids and was therefore omitted. The method provided a 15-minute run time and reliable quantitation across a broad PFAS spectrum.

Benefits and Practical Applications

The developed protocol offers a fast, cost-effective approach for routine PFAS monitoring in food matrices. It balances simplicity with robust clean-up, making it suitable for quality control laboratories and environmental testing facilities concerned with food safety.

Future Trends and Possibilities

Further developments may include extension to other food matrices, inclusion of isotope dilution standards for improved accuracy, high-resolution mass spectrometry for non-target PFAS screening, and automation of extraction workflows to increase throughput.

Conclusion

A comprehensive LC–MS/MS method was established for forty PFAS in carrot samples, combining a streamlined extraction, optimized SPE clean-up, and rapid chromatographic analysis. The approach demonstrated strong recoveries, minimal matrix interference, and applicability for routine monitoring.

References

Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS; Draft Method 1633, EPA (June 2022).