Robust and Reproducible Monitoring of PFAS in Treated Wastewater by Direct Injection on 6495D LC/MS

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants that resist heat, water and oils. Their widespread use in industrial and consumer products has led to global dissemination, posing health and ecological risks. Monitoring PFAS in treated wastewater is essential to prevent their release into drinking water sources and sensitive ecosystems.

Objectives and Study Overview

This application note evaluates a direct-injection workflow on the Agilent 6495D triple quadrupole LC/MS for quantifying 38 PFAS in treated industrial wastewater. The study aims to demonstrate a rapid 17-minute analysis, robust performance across repeated injections, low detection limits, and sensitivity at sub-nanogram per liter levels.

Methodology

A single aliquot of treated wastewater was spiked with 38 target PFAS at 10 ng/L and nine isotopically labeled surrogates. After a 1:1 dilution with methanol, samples were directly injected (20 µL) without extensive cleanup. Calibration standards ranged from 0.5 to 100 ng/L, and additional spikes at 1 ng/L assessed sensitivity.

Instrumentation Used

• Agilent 1290 Infinity II LC system with Poroshell AQ-C18 column (4.6 × 100 mm, 2.7 µm) at 45 °C
• Mobile phases: water with 5 mM ammonium acetate (A) and methanol (B); flow rate 0.5 mL/min; gradient of 20–90% B over 14.4 min
• Agilent 6495D Triple Quadrupole MS with Jet Stream source; dynamic MRM in positive/negative modes
• Optimized source conditions: drying gas 12 L/min at 250 °C, sheath gas 12 L/min at 370 °C, capillary voltage ±2.35–3.0 kV

Key Results and Discussion

Linearity was excellent (R2 ≥ 0.995) across 0.5–100 ng/L for all 38 analytes. Method detection limits ranged from 0.25 to 3.4 ng/L, with most PFAS below 1 ng/L. Over 150 consecutive injections of a 10 ng/L wastewater spike, relative standard deviations remained between 4 and 19%, meeting typical environmental testing criteria (< 20% RSD). A 1 ng/L spike in wastewater enabled the clear detection of over 30 PFAS against a clean baseline.

Benefits and Practical Applications

Direct injection eliminates labor-intensive cleanup, boosts sample throughput and reduces consumable costs while preserving analytical sensitivity. The workflow supports regulatory monitoring programs and high-throughput environmental laboratories by delivering reliable quantitation at low ng/L levels for multiple PFAS.

Future Trends and Applications

Advancements may include coupling direct-injection methods with high-resolution mass spectrometry for non-target screening, automating sample handling to further increase throughput, and extending analyses to other challenging matrices such as sludge or groundwater. Emerging regulations will drive demand for broader PFAS panels and lower detection thresholds.

Conclusion

The Agilent 6495D LC/MS with direct injection achieves robust, reproducible quantitation of 38 PFAS in treated wastewater within 17 minutes. Excellent linearity, low detection limits and consistent RSDs across 150 injections demonstrate the method’s suitability for high-throughput environmental monitoring at trace levels.