Analysis of Aliphatic Hydrocarbons in Diesel and Gasoline Range Organics in Ground and Surface Water by GC/MS

Significance of the Topic

Environmental contamination by aliphatic hydrocarbons such as diesel range organics (DROs) and gasoline range organics (GROs) poses risks to human health and aquatic ecosystems. Accurate monitoring of these compounds in ground and surface water is essential for regulatory compliance and environmental protection.

Objectives and Study Overview

This study evaluates the suitability and performance of the Thermo Scientific TraceGOLD TG-5SilMS column when coupled with a GC/MS system for the analysis of aliphatic hydrocarbons in water according to US EPA Method 8015.

• Assess chromatographic separation and sensitivity for DROs and GROs (C13–C35).
• Demonstrate compliance with EPA method requirements for environmental monitoring.

Methodology and Instrumentation Used

A pre-mixed alkane standard (1 ng/µL in hexane) covering carbon chains C13–C35, including internal standards pristane and phytane, was analyzed. Key instrumentation and conditions included:

• Gas Chromatograph: Thermo Scientific TRACE GC Ultra with TraceGOLD TG-5SilMS column (30 m × 0.25 mm × 0.25 µm) and 2 m guard column.
• Autosampler: Thermo Scientific TriPlus Autosampler, 1 µL splitless injection, injector at 275 °C, split flow 30 mL/min.
• Oven Program: 60 °C hold 5 min; ramp 8 °C/min to 300 °C; hold 10 min; helium carrier at 1.5 mL/min.
• Mass Spectrometer: Thermo Scientific Ion Trap MS ITD 230 LT; EI+ segmented scan 45–450 amu; source 225 °C, 70 eV.
• Data Processing: Thermo Scientific Xcalibur software.

Key Results and Discussion

Baseline resolution of all target hydrocarbons (C13–C35) and internal standards was achieved, with narrow peaks and minimal tailing. The low-polarity silarylene phase of the TG-5SilMS column provided high selectivity and reproducible retention times. While EPA Method 8015 typically uses GC/FID detection, the GC/MS configuration enhanced compound identification and confirmation.

Benefits and Practical Applications

• Regulatory Compliance: Fully meets US EPA Method 8015 criteria for DRO and GRO analysis in water matrices.
• Detection Flexibility: Compatible with both FID and MS for screening and confirmatory workflows.
• Robust Separation: High peak integrity reduces quantitation uncertainties.
• Workflow Efficiency: Automated sample introduction and integrated data handling streamline routine analysis.

Future Trends and Potential Applications

• Adoption of high-resolution mass spectrometry for lower detection limits and enhanced deconvolution of complex mixtures.
• Expansion to aromatic hydrocarbons and polycyclic aromatic hydrocarbons for comprehensive environmental profiling.
• Development of automated, in-situ monitoring systems for near real-time water quality assessment.
• Application in industrial process control for fuel quality assurance and spill remediation monitoring.

Conclusion

The Thermo Scientific TraceGOLD TG-5SilMS column paired with GC/MS delivers reliable, high-resolution separation and detection of aliphatic hydrocarbons in water samples, fulfilling the requirements of US EPA Method 8015. This approach provides environmental laboratories with a robust tool for accurate monitoring of DROs and GROs.

Reference

1. US EPA Method 8015: Determination of Nonhalogenated Organics by Gas Chromatography.