Improve Trace Analysis of Acetylene, Propadiene, and Methyl Acetylene Impurities with Higher Capacity Alumina MAPD Columns

Importance of the Topic

Trace analysis of acetylene, propadiene and methyl acetylene in light hydrocarbon streams is critical for protecting polymerisation catalysts and ensuring product quality. Low-level polar impurities can coelute with major components in gas chromatography, leading to inaccurate quantification and potential process upsets. Improving column capacity and deactivation chemistry helps to minimize peak tailing, enhance resolution and extend the linear detection range.

Objectives and Study Overview

This study compares the performance of a new Rt®-Alumina BOND/MAPD PLOT column with a conventional Select Al2O3 MAPD column. Key aims include evaluating absolute retention, peak symmetry under increasing sample volume, and linearity for trace-level impurities. The goal is to demonstrate that improved deactivation and higher capacity provide more reliable trace analysis in QA/QC of petroleum gases.

Methodology and Instrumentation

Sample volumes from 5 µL to 250 µL of a QA test mixture (C1–C5 hydrocarbons with polar impurities) were injected using a six-port valve and variable loop sizes. An isothermal GC method was applied:

• Column dimensions: 50 m × 0.53 mm ID × 10 µm film thickness
• Oven temperature: 130 °C (Rt®-Alumina) or 100 °C (Select Al2O3 for optimized capacity)
• Carrier gas: helium at 30 kPa (4.4 psi)
• Injector: split, 200 °C, split flow 80 mL/min
• Detector: flame ionisation detector (FID) at 200 °C

Key Results and Discussion

Absolute retention on the Rt®-Alumina BOND/MAPD column increased separation space and eliminated coelutions observed on the Select Al2O3 column under comparable conditions. Peak tailing factors (USP) remained below 1.2 for propadiene and acetylene up to 100 µL injections on the new column, versus tailing factors exceeding 2.5 at large volumes on the conventional column. Symmetrical peaks persisted over a wide volume range, indicating effective deactivation and higher loadability. Linearity plots showed excellent correlation coefficients (>0.999) for all target impurities across the tested concentration range.

Benefits and Practical Applications

The enhanced Rt®-Alumina BOND/MAPD column offers:

• Greater capacity to accommodate larger sample volumes without loss of peak integrity
• Improved peak symmetry for accurate quantification of trace polar compounds
• Extended linear range suitable for QA/QC labs using less sensitive detectors
• Reliable separation of C1–C5 hydrocarbons and problematic impurities to prevent catalyst fouling

Future Trends and Applications

Continued advances in column deactivation and high-capacity stationary phases will further improve trace detection in complex gas matrices. Integration with mass spectrometry and microfluidic GC platforms may enable faster turnaround and in-field testing. Novel materials offering tailored selectivity for emerging contaminants could expand applications in environmental monitoring and petrochemical process control.

Conclusion

The new Rt®-Alumina BOND/MAPD column demonstrates superior capacity and deactivation compared with conventional MAPD phases. It delivers sharper, more symmetric peaks for acetylene, propadiene and methyl acetylene at trace levels, enabling accurate quantification and robust QA/QC workflows in petroleum gas analysis.