A Single Calibration Method for Water AND Soil Samples Performing EPA Method 8260

Significance of the Topic

Environmental laboratories analyzing volatile organic compounds (VOCs) under USEPA Method 8260 face complex calibration and quality-control demands across diverse sample matrices. Streamlining these workflows without sacrificing data integrity is crucial to reduce turnaround times, lower operational costs, and maintain regulatory compliance.

Objectives and Study Overview

This application note by Anne Jurek (EST Analytical) introduces a patented automated sampling mode that allows water samples to be processed in soil‐mode on a single autosampler. The goal is to eliminate separate calibration curves, standards, and blanks for water versus soil, thus simplifying routine laboratory analysis under Method 8260.

Methodology

The procedure employs a three-step automated sequence:

• Empty vials and water samples or standards are loaded in separate trays. An empty vial is transferred to the soil sampling station.
• A helium pressure is applied to the water vial, a defined volume is withdrawn, and internal standard is added before transferring to the soil station vial.
• The sample is heated and purged identically to a soil sample, trapping analytes on a thermal desorption trap, which is then desorbed into the GC column.

Calibration was performed with a nine-point curve (0.5–200 ppb), method detection limits (MDLs) were determined at the low standard, and accuracy/precision were assessed at midpoint concentrations.

Instrumentation

The study used:

• EST Analytical Centurion WS autosampler
• EST Evolution purge-and-trap concentrator with Vocarb 3000 trap
• Agilent 7890A GC coupled to a 5975 inert XL MS
• Restek Rxi-624Sil MS column (30 m × 0.25 mm × 1.4 µm)

Key purge-trap parameters included 11 min purge at 40 mL/min, trap bake at 270 °C, and desorb at 260 °C. GC oven program ran from 45 °C to 220 °C at 15 °C/min.

Main Results and Discussion

The water-in-soil mode exhibited excellent linearity (R² > 0.99) across 0.5–200 ppb. MDLs met Method 8260 criteria. Precision averaged 0.16 % RSD and recoveries averaged 104.9 %, demonstrating reliable performance comparable to traditional water-mode analyses.

Benefits and Practical Applications

By unifying water and soil sampling parameters, laboratories can:

• Reduce calibration and standard preparation by half
• Minimize instrument downtime and consumable use
• Accelerate sample throughput and increase profitability

Future Trends and Potential Applications

Further developments may extend this unified sampling approach to additional matrices (e.g., sludge, air) and integrate with laboratory information management systems (LIMS) for fully automated data reporting. Advances in trap technology and autosampler flexibility will continue to drive efficiency in environmental VOC analysis.

Conclusion

The patented Centurion WS water extraction mode in soil configuration provides a robust, compliant, and time-saving alternative for Method 8260 analyses. It meets all regulatory requirements while significantly reducing the number of required calibration curves, standards, and blanks.

References

• United States Environmental Protection Agency. Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS); Method 8260B, Revision 2, December 1996.