South Louisiana Crude Oil on Rxi®-1HT (15 m x 0.25 mm x 0.10 μm)

Importance of the Topic

Detailed compositional analysis of crude oil is vital for industrial applications including quality control, process optimization, and regulatory compliance. High-temperature gas chromatography (HTGC) enables robust separation of high-boiling hydrocarbon fractions, providing critical insights into the carbon chain distribution of complex samples such as South Louisiana crude oil.

Objectives and Study Overview

The primary goal of this study was to evaluate the performance of a 15 m × 0.25 mm × 0.10 µm Rxi-1HT capillary column for profiling mid- to high-boiling hydrocarbon components in South Louisiana crude oil. Retention times for representative n-alkanes (C10, C20, C30) were recorded to assess chromatographic resolution and reproducibility.

Methodology

A crude oil sample was diluted to 50,000 ng/µL in methylene chloride and injected (1 µL split, 10:1) using a premium wool-packed liner at 275 °C. The oven program ramped from 40 °C (0.1 min hold) to 400 °C at 20 °C/min, holding for 1.9 min. Hydrogen served as the carrier gas at a constant flow of 1.75 mL/min. Data were acquired at 20 Hz to ensure high signal fidelity for narrow high-temperature peaks.

Instrumentation Used

• Gas chromatograph: Agilent/HP 6890 GC
• Column: Restek Rxi-1HT, 15 m × 0.25 mm ID, 0.10 µm film (actual length 15.7 m)
• Detector: Flame ionization detector at 420 °C
• Carrier gas: H₂ (1.75 mL/min)
• Make-up gas: N₂ (50 mL/min), H₂ (40 mL/min), air (450 mL/min)

Main Results and Discussion

The measured retention times were 119.5 s for C10, 456.2 s for C20, and 678.0 s for C30, reflecting effective separation across a broad boiling range. The thin film thickness and high operational temperature capability of the Rxi-1HT phase facilitated narrow peak widths and reduced band broadening. These characteristics support reliable quantitation of heavy hydrocarbon fractions in a single run.

Benefits and Practical Applications

• Rapid profiling of crude oil hydrocarbon distributions for quality assurance.
• Enhanced resolution of mid- and high-boiling components in refinery streams.
• Support for process troubleshooting and feedstock evaluation in petrochemical industries.

Future Trends and Applications

Integration of HTGC with mass spectrometry will improve structural identification of isomeric and branched hydrocarbons. Automated sample preparation and data processing workflows are expected to accelerate analysis throughput. Advances in stationary phase chemistry may extend operational temperature limits, further enhancing high-boiling compound separation.

Conclusion

This application note demonstrates that the Rxi-1HT column provides rapid, reproducible separation of crude oil n-alkanes from C10 through C30 under a single temperature program. The method delivers critical data for refining operations and quality control, supporting informed decision-making in petrochemical industries.