Analysis of Total Petroleum Hydrocarbons using Temperature Programmed Large Volume Injection

Importance of the Topic

Monitoring total petroleum hydrocarbons (TPH) in environmental and food matrices is essential for assessing contamination, ensuring regulatory compliance and protecting human health. Traditional sample enrichment via rotary evaporation can be time-consuming and prone to losses. Implementing large volume injection (LVI) with temperature-programmed vaporization streamlines preparation, boosts sensitivity at trace levels and enhances laboratory throughput.

Objectives and Overview

This study evaluates a GC-FID method for TPH analysis using a Scion 456-GC system equipped with a programmable temperature vaporizer (PTV) and large volume injection. The aim is to meet DIN-EN-ISO 9377-2 standards while simplifying sample prep, improving recovery and delivering rapid, precise quantification of C10–C44 hydrocarbons in soils and waters.

Methodology

Samples are extracted with n-hexane either by traditional solvent extraction or in-vial extraction. A calibration standard of n-alkanes (C10–C44) in hexane and a quality control reference (RIVM mineral oil standard) are prepared. Injection is performed in “at-once” LVI mode: the PTV inlet is held at the solvent’s boiling point, the split vent remains open for initial solvent venting, then closes and the temperature ramps to transfer analytes onto the column. Chromatographic separation is achieved on a Select™ Mineral Oil column under a multi-step oven program, with helium carrier gas and FID detection.

Instrumentation Used

• Scion 456-GC gas chromatograph
• Programmable Temperature Vaporizer (PTV) inlet with packed large volume injection liner
• Scion Select Mineral Oil GC column (15 m × 0.32 mm × 0.5 µm)
• FID detector (350 °C)
• CP-8400 autosampler for precise 70 µL injections

Results and Discussion

Calibration across C10–C44 alkanes showed linear detector response. Discrimination ratios (C10/C20 and C40/C20) remained within the acceptable 0.8–1.2 range, confirming minimal volatility bias. Repeatability testing of the RIVM reference (n=8) yielded relative standard deviations of 0.72% (C10–C20) and 0.64% (C20–C40). Total run time per analysis was 12.25 minutes, demonstrating high throughput without extensive sample concentration steps.

Benefits and Practical Applications

• Elimination of separate evaporation step reduces sample handling and potential analyte loss
• High injection volumes improve detection limits for trace-level TPH
• Excellent precision supports QA/QC in environmental and industrial laboratories
• Short analysis time increases daily sample capacity

Future Trends and Potential Uses

Advances may include coupling LVI-PTV with mass spectrometry for improved compound identification, development of portable GC systems for field screening, and adaptation of the method to emerging hydrocarbon contaminants. Automated data processing and integration into laboratory information management systems will further streamline workflows.

Conclusion

The optimized temperature-programmed LVI-GC-FID method provides reliable, rapid and precise quantification of total petroleum hydrocarbons in environmental samples. It aligns with international standards while reducing sample preparation complexity and enhancing laboratory efficiency.

Reference

• National Institute for Public Health and the Environment (RIVM), Mineral Oil Reference Sample (CP741970).