Robustness Evaluation of PFAS Analysis in Soil Using LC-MS/MS

Importance of the topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants that accumulate in soil and can enter the food chain, posing risks to human health. Their chemical stability requires highly sensitive and robust analytical techniques to detect trace levels in complex matrices such as agricultural soils.

Objectives and Study Overview

This study evaluates the robustness of an LC-MS/MS method for simultaneous analysis of 30 PFAS in soil using the Shimadzu LCMS-8060RX system. The method was challenged by performing 500 consecutive injections of a soil matrix spiked at 0.1 µg/L to assess repeatability, detection limits, and recovery over extended operation.

Methodology and Instrumentation

Sample preparation followed a modified protocol from the National Agricultural and Food Research Organization, with soil extracts containing over 90 percent matrix. Key analytical conditions included ultrahigh-performance liquid chromatography on a C18 column, a PFAS delay column to minimize background contamination, and ESI in negative MRM mode. Calibration curves across six levels (0.01 to 10 µg/L) were constructed in triplicate. Instrumental parameters:

• UHPLC Nexera-X3 with Shim-pack Scepter C18-120 column
• Delay column for PFAS contamination control
• Mobile phases: 2 mM ammonium acetate in water and methanol
• Shimadzu LCMS-8060RX with ESI source, negative ion mode, MRM scanning
• Flow rate 0.3 mL/min, column temperature 40 °C, run time 20 min

Key Results and Discussion

The method achieved baseline separation of 30 PFAS in about 12 minutes with peak shapes maintained throughout 500 injections. Calibration curves showed r2 values above 0.996 for most analytes. Peak area repeatability (%RSD) remained below 8.5 for all compounds; detection limits ranged from 0.011 to 0.020 µg/L. Recoveries from QC samples stayed between 80 and 120 percent over the entire sequence, demonstrating sustained performance in a heavily loaded matrix.

Benefits and Practical Applications

The validated method offers analysts a reliable tool for routine monitoring of PFAS in soils, supporting environmental risk assessments, regulatory compliance, and remediation efforts. Its high throughput and robustness reduce downtime and maintenance related to PFAS carryover.

Future Trends and Applications

Emerging trends include coupling ion mobility spectrometry for enhanced isomer separation, expanding target lists to novel polyfluoroalkyl substances, and integrating high-resolution MS for non-target screening. Automated sample preparation and green solvent systems may further streamline PFAS analysis.

Conclusion

The LCMS-8060RX platform with a dedicated delay column and optimized MRM method demonstrated excellent stability and sensitivity for PFAS determination in challenging soil matrices over extended runs, making it a valuable solution for environmental laboratories.

Reference

1 Basic research on the movement of PFOA, PFOS, and other PFAS in agricultural environments into products
2 DRAFT METHOD 202201 Determination of perfluoroalkyl and polyfluoroalkyl substances in soil