U.S. EPA Method 625.1 – New Method and New Instrumentation for Semi-volatiles with Solid Phase Extraction

Importance of the Topic

The determination of semi-volatile organic compounds (SVOCs) in municipal and industrial wastewater is critical for environmental monitoring and regulatory compliance. U.S. EPA Method 625.1 defines procedures to quantify a broad list of acidic, basic and neutral SVOCs, including polycyclic aromatic hydrocarbons, chlorinated hydrocarbons, pesticides and nitroaromatic compounds. Automating sample preparation enhances data quality, reduces laboratory workload and minimizes solvent use and waste.

Objectives and Study Overview

This study evaluates an automated one-pass solid phase extraction (SPE) workflow for compliance with EPA Method 625.1. The aim is to demonstrate that a mixed-mode Atlantic® One-Pass SPE disk, coupled with a carbon cartridge and automated hardware, can extract the full range of target analytes with a single pH adjustment. A series of synthetic and real water samples were processed to verify method performance under diverse matrices.

Methodology and Instrumentation

The extraction protocol was performed on a Biotage® Horizon 5000 automated SPE system. Key features include:

• SPE disk: Atlantic® 8270 One-Pass mixed-mode disk (47 mm) combined with an 8270 Max Detect carbon cartridge
• Sample acidification to pH 2 to retain acidic, neutral and basic analytes on the disk and cartridge in one pass
• Elution steps: acetone/methylene chloride for acidic and neutral compounds; acetone/methylene chloride with 1% ammonium hydroxide for basic analytes; final elution of light-end SVOCs from the carbon cartridge
• Solvent drying and concentration using Biotage® DryVap in-line system with DryDisk® separation disks
• Analysis by GC/MS: Agilent 6890 gas chromatograph with 5973 mass selective detector, using a Zebron™ ZB-Semivolatiles column and a temperature program from 45 °C to 318 °C

Main Results and Discussion

Initial compliance experiments using synthetic water verified that all method demonstration criteria were met. Subsequent analysis of a synthetic wastewater sample yielded average recoveries between 64 % and 98 % for target analytes, with relative percent differences generally below 15 %. Both acidic and basic compounds showed consistent elution from the mixed-mode disk, while light-end SVOCs were efficiently recovered from the carbon cartridge. These results confirm that the one-pass configuration meets EPA acceptance ranges and provides reproducible data across multiple sample types.

Benefits and Practical Applications

• The automated one-pass SPE workflow reduces solvent consumption and hazardous waste generation compared to multi-pass liquid-liquid extraction
• Mixed-mode SPE disk simplifies sample preparation by combining acid, base and neutral extractions into a single step
• Automation improves throughput, data accuracy and reproducibility, facilitating routine compliance monitoring in environmental, industrial and QA/QC laboratories

Future Trends and Potential Applications

Continued integration of automated SPE with advanced detection platforms could expand the method to emerging contaminants and complex matrices. Miniaturized and high-throughput SPE devices may further reduce solvent usage and processing time. Additionally, coupling with liquid chromatography–tandem mass spectrometry (LC-MS/MS) could broaden the range of detectable polar semi-volatiles, meeting evolving regulatory needs.

Conclusion

The automated one-pass SPE approach using an Atlantic® One-Pass mixed-mode disk and carbon cartridge delivers a robust, efficient and compliant workflow for EPA Method 625.1. It offers consistent analyte recoveries across diverse water matrices, simplifies sample handling, and enhances laboratory productivity.

References

• U.S. EPA Method 625.1: Determination of Semi-volatile Organic Compounds in Wastewaters
• Biotage NACRW 2018 Application Note, Part Number P185.V.1