Analysis of Total Petroleum Hydrocarbons in Environmental Samples Using Ultra-Fast Gas Chromatography

Importance of the Topic

The analysis of total petroleum hydrocarbons (TPH) in environmental matrices is essential for assessing contamination levels, guiding remediation efforts, and ensuring compliance with regulatory standards such as ISO 16703.

Objectives and Overview

This application note describes the development of an ultra-fast gas chromatography (UFGC) method using the Agilent Intuvo 9000 GC to quantify TPH in soil and sediment reference materials. The goal was to achieve a three-minute analysis while satisfying ISO 16703 criteria for accuracy, precision, and selectivity.

Methodology and Instrumentation

• Sample Preparation
  
  • Reference Materials: BAM-U021 (soil) and BAM-U022 (river sediment).
  • Extraction: 15 g sample ultrasonically extracted with acetone and C10–C40 retention time window standards.
  • Cleanup: Centrifugation, two 100 mL water washes, drying over Na₂SO₄, and Florisil SPE cleanup.
• Instrumentation
  
  • Gas Chromatograph: Agilent Intuvo 9000 Series with direct column heating technology.
  • Column: DB-5ht, 5 m × 0.32 mm, 0.1 µm film thickness.
  • Carrier Gas: Helium constant flow at 10 mL/min.
  • Temperature Program: 40 °C hold 0.5 min; ramp at 250 °C/min to 350 °C; hold 1.3 min.
  • Inlet: Splitless at 350 °C with tapered deactivated liner.
  • Detector: Flame ionization detector at 350 °C.
  • Autosampler: Agilent 7693 ALS with 10 µL syringe.

Main Results and Discussion

• System Suitability
  
  • Baseline resolution of even-numbered C10–C40 alkanes in heptane.
  • Recoveries ranged from 0.93 to 1.01 relative to C20, exceeding the 0.80 minimum.
• Calibration
  
  • Six-level calibration (0.24–8.00 mg/mL) using mineral oil standards achieved R² = 0.9998.
  • Repeatability RSD of 1.7% for a 1 mg/mL standard (below the 5% limit).
• Sample Analysis
  
  • Ten replicate injections per duplicate sample, total run time ~3 minutes.
  • Retention time RSD for C10 and C40 markers: 0.11% and 0.02%, respectively.
• Quantitative Performance
  
  • BAM-U021 (soil): 3,500 ± 28 mg/kg vs certified 3,560 ± 260 mg/kg (RSD ≤ 0.82%).
  • BAM-U022 (sediment): 8,709 ± 32 mg/kg vs certified 8,270 ± 550 mg/kg (RSD ≤ 1.37%).
  • Experimental repeatability (r) values of 59 and 126 mg/kg are below ISO limits (136 and 337 mg/kg).

Benefits and Practical Applications

• Sub-three-minute analyses improve laboratory throughput and reduce costs.
• Direct column heating ensures precise temperature control without complex ovens.
• Method fully complies with ISO 16703 requirements for selectivity, resolution, and repeatability.

Future Trends and Possibilities

• Extension to other environmental matrices and broader hydrocarbon ranges.
• Integration with mass spectrometry or advanced detectors for speciation.
• Enhanced automation and data processing for streamlined workflows.

Conclusion

The UFGC method on the Agilent Intuvo 9000 achieves reliable, three-minute TPH quantification in environmental samples, meeting ISO 16703 performance benchmarks and demonstrating excellent accuracy and precision on certified reference materials.

References

• ISO 16703:2004(E). Soil quality – Determination of hydrocarbon content (C10–C40) by gas chromatography.
• Sigma-Aldrich Company. ISO 16703 sample preparation kit (p/n 56681-1KT-F).