Evaluating System Robustness of a High-Sensitivity Triple Quadrupole LC/MS for PFAS Analysis in Food Matrix Over an Extended Period

Importance of PFAS Analysis in Complex Food Matrices

Per- and polyfluoroalkyl substances (PFAS) are subject to increasingly stringent regulations due to their persistence and potential health risks. Analytical laboratories require highly sensitive and robust methods to detect trace levels of PFAS in challenging matrices such as food. Maintaining instrument uptime and consistent performance under high-throughput conditions is essential for meeting current and future regulatory demands.

Objectives and Study Overview

The study aimed to assess the long-term robustness of a high-sensitivity triple quadrupole LC/MS system for targeted PFAS analysis in a complex salmon matrix. Key goals included:

• Monitoring instrument performance over approximately 3 weeks of continuous operation.
• Evaluating signal stability for two representative PFAS compounds: PFOA and PFOS.
• Determining the impact of extensive matrix exposure on sensitivity and maintenance requirements.

Methodology

Salmon was chosen as a demanding food matrix. Sample preparation involved:

• Grinding fresh salmon and extracting 5 g with water and acetonitrile using QuEChERS salts and ceramic homogenizers.
• Centrifugation and cleanup on a Captiva EMR PFAS Food II cartridge.
• Spiking the extract with native and isotopically labeled PFAS standards to yield ~0.5 ppb equivalent concentration.
• Repeated injections of the spiked matrix to track performance after each 1 mL of extract injected (100 injections at 10 µL each).

Used Instrumentation

An Agilent 1290 Infinity II LC system coupled to an Agilent 6495D triple quadrupole mass spectrometer was employed. Key parameters included:

• Ionization: AJS electrospray in negative mode; drying gas at 160 °C/18 L·min⁻¹; sheath gas at 390 °C/11 L·min⁻¹; nebulizer at 24 psi.
• MS settings: capillary voltage 2400 V, detector gain factor 5; multiple reaction monitoring based on prior optimized transitions.
• LC conditions: short C18 guard and analytical columns with a PFC delay column; mobile phases water with 2 mM ammonium acetate (A) and acetonitrile (B); 0.8 mL·min⁻¹ flow at 45 °C; 3 min gradient (20–90% B).

Key Results and Discussion

The system underwent 13 700 injections of salmon extract (total ~137 mL) without any maintenance. Observations included:

• Raw peak areas for PFOA and PFOS remained within ±20% of the mean, with RSDs of 3.7% and 5.3%, respectively.
• Internal standard correction reduced variability further, yielding RSDs below 5% for both analytes.
• Regular instrument calibrations (mass axis and peak width) passed manufacturer criteria without retuning.
• Despite significant matrix deposits observed on the inlet, no drop in sensitivity or signal quality occurred.

Benefits and Practical Applications

The demonstrated robustness offers:

• High-throughput PFAS screening with minimal downtime.
• Reliable quantitation in complex food samples for regulatory compliance.
• Cost savings by extending maintenance intervals without performance loss.
• Confidence in long-term data quality for QA/QC laboratories.

Future Trends and Opportunities

Advances may include integration of automated maintenance routines, expansion to broad PFAS panels, coupling with high-resolution techniques for unknown screening, and applying machine learning to predict maintenance needs based on performance drift. Miniaturized flow paths and novel ion source designs may further enhance robustness under heavy matrix loads.

Conclusion

This study confirms that a 6495D triple quadrupole LC/MS system can sustain high-sensitivity PFAS analysis in a challenging food matrix over extended continuous operation. The method delivered stable, low-variance results with no instrumental tuning or maintenance, supporting its use in demanding regulatory and high-throughput environments.