Quantification of Liquid Hydrocarbons with Large Boiling Point Range using the Polyarc Reactor

Significance of the topic

Accurate quantification of complex hydrocarbon mixtures across a wide boiling point range is essential in many fields including petrochemical analysis, environmental monitoring, and quality control. Traditional gas chromatography–flame ionization detection (GC-FID) requires calibration curves for each compound, which is time-consuming and may introduce errors when mixtures differ from standards. The Polyarc® reactor offers a solution by converting all hydrocarbons to methane, yielding a uniform FID response per carbon atom and eliminating the need for individual calibration standards.

Objectives and study overview

This study evaluates the performance of a GC system equipped with a Polyarc® reactor for quantifying C5 to C18 n-alkanes without calibration standards. Key aims include assessing accuracy, separation efficiency, and the reactor’s ability to detect and correct common GC inlet issues such as preferential vaporization and leaks.

Methodology

A mixture of 13 n-alkanes (C5–C18) spanning 2.4 to 21.1 wt% was injected in splitless mode onto an Agilent 7890A GC system. The sample passed through either a traditional FID or a Polyarc®/FID configuration. N-decane served as an internal standard. The injector and column conditions were optimized to maintain constant inlet pressure and sufficient flow to prevent discrimination of volatile components.

Instrumental setup

• Gas chromatograph: Agilent 7890A with split/splitless inlet
• Reactor: Polyarc® ARC PA-RRC-A02 with manual flow module PA-CAS-A07
• Carrier gas: Helium (99.999%)
• FID gases: Hydrogen (99.999%) and zero-grade air
• Column: Rtx-2887, 10 m × 0.53 mm, 2.65 µm film thickness
• Inlet temperature: 360 °C; oven ramp: 35 °C to 245 °C at 15 °C/min

Main results and discussion

The Polyarc®/FID system achieved an average quantification error of 0.9% and a maximum error of 2.4% relative to known concentrations. Peak width (FWHM) increased by only 9% compared to FID-only analysis, demonstrating minimal loss of separation efficiency. Experiments at reduced inlet pressure (3.33 psi vs. 6.64 psi) revealed systematic under-reporting of low-boiling analytes due to preferential vaporization. Standard mixture analysis with Polyarc® allowed identification and correction of injection conditions and detection of column fitting leaks.

Benefits and practical applications

• Eliminates the need for compound-specific calibration standards
• Delivers uniform detector response per carbon atom for diverse hydrocarbons
• Simplifies routine quantification and reduces analysis time
• Enables detection of inlet and column issues such as discrimination and leaks
• Applicable in petrochemical quality control, environmental analysis, and process monitoring

Future trends and opportunities

Future developments may extend Polyarc® technology to more complex mixtures including aromatic and heteroatom-containing compounds. Integration with online and real-time monitoring platforms can further enhance process analytics. Continued refinement of reactor design and flow control will broaden the applicability to high-throughput industrial laboratories.

Conclusion

The Polyarc® reactor coupled with GC-FID provides a robust, accurate, and efficient method for quantifying hydrocarbons over a wide boiling range without calibration standards. Its ability to detect and correct inlet artifacts further improves data reliability, making it a valuable tool across analytical laboratories.

References

1. Scanlon JT, Willis DE. Journal of Chromatographic Science, 23 (1985) 333–340.