Semivolatile Organics in Drinking Water on Rxi®-5Sil MS by EPA Method 525.2

Significance of the Topic

Semivolatile organic compounds in drinking water pose significant health and regulatory concerns due to their persistence, bioaccumulation potential, and toxicity. Reliable, high-throughput analytical methods are essential for monitoring compliance with environmental standards and safeguarding public health.

Objectives and Study Overview

This application note illustrates the use of EPA Method 525.2 to analyze a broad range of semivolatile organics—including pesticides, polycyclic aromatic hydrocarbons, phthalates, and nitroaromatics—in drinking water. The goal is to demonstrate chromatographic separation, identification, and quantification of over 90 target compounds using a single gas chromatography–mass spectrometry (GC–MS) setup.

Methodology and Instrumentation

• Sample preparation: Method 525.2 semivolatile mix with internal (IS) and surrogate standards (SS) in acetone; concentrations at 8 µg/mL (IS/SS at 25 µg/mL).
• Injection: 1 µL pulsed splitless (hold 0.59 min) at 270 °C; pulse pressure 30 psi; purge flow 100 mL/min.
• Oven temperature program: 50 °C (1 min) → 285 °C at 30 °C/min → 305 °C at 3 °C/min → 320 °C at 30 °C/min (hold 1 min).
• Carrier gas: Helium, constant flow 1.2 mL/min (linear velocity 39.7 cm/s at 40 °C).
• Detection: Quadrupole MS in scan mode (35–550 amu) with electron ionization; transfer line at 280 °C, source at 270 °C, quad at 150 °C; scan rate 5.36 scans/sec.

Used Instrumentation

• Gas chromatograph: Agilent 7890A GC.
• Mass spectrometer: Agilent 5975C MSD.
• Column: Rxi-5Sil MS, 30 m × 0.25 mm I.D., 0.25 µm film thickness.
• Liner: Premium 4 mm single taper with wool.
• Ionization mode: Electron Ionization (EI), DFTPP tune.

Main Results and Discussion

• Baseline separation achieved for 95 semivolatile analytes within a 36-minute run, including isophorone, pesticides, phthalates, and multiple PAHs.
• Internal and surrogate standards provided accurate quantification and recovery monitoring; recoveries met EPA acceptance criteria.
• Retention time reproducibility and mass spectral fidelity ensured reliable compound identification and minimized false positives.

Benefits and Practical Applications

• Comprehensive, single-run analysis streamlines laboratory workflows and boosts sample throughput.
• Method compliance with EPA 525.2 supports regulatory reporting for drinking water monitoring programs.
• Flexible platform allows integration of additional or emerging semivolatile contaminants with minimal method adaptation.

Future Trends and Applications

Advances in high-resolution and tandem mass spectrometry promise greater sensitivity and selectivity for trace-level semivolatiles. Emerging sample preparation techniques—such as microextraction and solid-phase microextraction—aim to reduce solvent use and enhance detection limits. Automation, miniaturized GC–MS systems, and data-processing algorithms will further accelerate routine monitoring and enable on-site water quality assessments.

Conclusion

EPA Method 525.2 on an Rxi-5Sil MS column offers a robust, reproducible, and regulatory-compliant approach for monitoring a broad spectrum of semivolatile organic contaminants in drinking water. Its proven performance supports high-throughput laboratories in environmental and public health applications.

Reference

1. Restek Corporation. Semivolatile Organics in Drinking Water on Rxi-5Sil MS by EPA Method 525.2. Application Note GC_EV1247.