Florida TRPH Standard on Rxi®-5HT (15 m x 0.25 mm x 0.10 μm)

Significance of the Topic

Quantification of total recoverable petroleum hydrocarbons (TRPH) across a wide carbon range is vital for environmental monitoring and regulatory compliance. Robust gas chromatographic methods ensure accurate profiling of hydrocarbon mixtures, guiding risk assessment and remediation efforts.

Objectives and Study Overview

This application note evaluates a standard mixture of hydrocarbons (C8–C40) on an Rxi-5HT GC column, aiming to demonstrate the column’s suitability for TRPH analysis and to establish retention behavior for regulatory reporting.

Methodology and Instrumentation

The analysis employed split injection of a 500 ng/µL TRPH standard in hexane. A short, narrow-bore Rxi-5HT column (15 m × 0.25 mm ID; 0.10 µm film) delivered sharp peaks across C8–C40. A hydrogen carrier gas at constant flow (1.75 mL/min) and a flame ionization detector (FID) at 420 °C provided sensitivity across the hydrocarbon range. Temperature programming from 40 °C (hold 0.1 min) to 400 °C at 19.6 °C/min (hold 1.53 min) ensured elution of high-boiling compounds within a reasonable runtime. Split injection (1 µL, ratio 250:1) prevented column overload while maintaining peak symmetry.

Used Instrumentation

• GC System: Agilent/HP 6890
• Column: Restek Rxi-5HT, 15 m × 0.25 mm ID, 0.10 µm film thickness
• Detector: Flame Ionization Detector at 420 °C
• Injection Liner: Premium 4 mm precision liner with wool

Main Results and Discussion

The method achieved baseline resolution of saturated hydrocarbons from C8 (tR 64.1 s) to C40 (tR 856.7 s). Retention times increased linearly with carbon number, confirming predictable elution profiles. The rapid temperature ramp minimized runtime while preserving peak shape. Consistent peak symmetry supported reliable quantitation across the carbon range.

Benefits and Practical Applications

• Efficient separation of TRPH components in a single run
• High sensitivity and reproducibility for environmental and industrial quality control
• Predictable retention behavior simplifies calibration and reporting

Future Trends and Potential Applications

Emerging trends include coupling high-temperature GC with mass spectrometry for enhanced identification of isomeric hydrocarbons, exploring alternative carrier gases to further improve separation efficiency, and integrating automated sample handling for high-throughput environmental screening.

Conclusion

The Rxi-5HT column, combined with optimized GC-FID parameters, offers a reliable platform for comprehensive TRPH analysis. Its broad temperature range and efficient chromatographic performance enable accurate quantification of C8–C40 hydrocarbons, supporting environmental monitoring and regulatory compliance.