Semivolatiles by EPA Method 525.2 on Rxi®-5ms

Significance of the topic

The determination of semivolatile organic compounds and pesticide residues in environmental and drinking water samples is crucial for ensuring public health and regulatory compliance. EPA Method 525.2 provides standardized conditions for liquid–liquid extraction followed by capillary gas chromatography–mass spectrometry (GC-MS), enabling sensitive and reproducible quantitation of a broad range of analytes at trace levels.

Objectives and Study Overview

This application employs EPA Method 525.2 on a Restek Rxi®-5ms capillary column to separate and detect 95 semivolatile compounds, including polycyclic aromatic hydrocarbons (PAHs), organochlorine, organophosphorus, nitrogen-containing pesticides, and phthalates. The study aims to demonstrate baseline resolution, linear response, and robust performance in a single run, facilitating multi-class analysis under a unified method.

Methodology and Instrumentation

Extraction and Sample Preparation

• Liquid–liquid extraction of water samples according to EPA 525.2 protocol
• Internal standards (IS) and surrogate standards (SS) spiked at 25 µg/mL; target analytes at 10 µg/mL

GC-MS Conditions

• Gas chromatograph: HP 6890 GC
• Column: Rxi®-5ms, 30 m × 0.25 mm ID, 0.25 µm film thickness
• Injection: 1 µL pulsed splitless (0.15 min hold), inlet at 250 °C, pulse pressure 50 psi, purge at 80 mL/min after 0.3 min
• Carrier gas: Helium, constant flow 1.2 mL/min
• Oven program: 90 °C (1 min) → 270 °C at 20 °C/min → 315 °C at 6 °C/min
• Mass spectrometer: HP 5973 MSD quadrupole
• Ionization: Electron ionization (EI), solvent delay 3.00 min, transfer line 280 °C
• Scan mode: full scan 35–550 amu, tune type DFTPP

Main Results and Discussion

The method achieved clear separation of all listed analytes, including early eluters such as isophorone and late eluters like benzo[ghi]perylene. Marker compounds across chemical classes displayed baseline resolution without coelution. Surrogate recoveries and internal standard responses indicated consistent instrument performance. The temperature program effectively eluted high-boiling compounds within 40 minutes, demonstrating throughput suitable for routine monitoring.

Benefits and Practical Applications

Using a single-column, single-injection approach under EPA 525.2 conditions:

• Enables broad-spectrum screening of semivolatiles and pesticide residues in water and environmental matrices
• Delivers sensitive detection with minimal matrix interferences via MS scan mode
• Reduces method development time by applying a standardized protocol
• Supports compliance testing for regulatory agencies and industrial laboratories

Future Trends and Applications

Advancements may include high-resolution mass spectrometry for improved selectivity, automated sample preparation to increase throughput, and miniaturized extraction techniques to reduce solvent use. Integration with data-processing software and cloud-based LIMS will enhance trend monitoring and rapid decision-making in environmental laboratories.

Conclusion

The application of EPA Method 525.2 on an Rxi®-5ms column coupled with GC-MS demonstrates a robust, versatile workflow for the simultaneous analysis of a diverse set of semivolatiles and pesticides. This validated method provides reliable quantitation, excellent chromatographic resolution, and operational efficiency required for routine environmental monitoring.

Reference

• EPA Method 525.2: Measurement of Semivolatile Organic Compounds in Drinking Water by Liquid–Liquid Extraction and Capillary Column Gas Chromatography/Mass Spectrometry, Revision 2.0
• Restek Application Note GC_EV00859: Semivolatiles by EPA Method 525.2 on Rxi®-5ms