Extending the Power of Stabilized PLOT Column Technology to Process GC Analyzers

Importance of the Topic

Porous layer open tubular (PLOT) columns play a pivotal role in petrochemical analysis by enabling rapid, high-resolution separation of volatile compounds. In continuous process gas chromatography (GC) applications, column stability and reproducibility are essential to ensure accurate, real-time monitoring of product streams and to maintain product quality and process safety.

Objectives and Study Overview

This study evaluates a new generation of metal MXT® PLOT columns featuring proprietary bonding techniques originally developed for fused silica. The primary goals are to compare the mechanical and thermal stability, flow reproducibility, phase bleed, and separation efficiency of MXT® PLOT columns against conventional metal PLOT columns under typical process-monitoring conditions.

Methodology and Instrumentation

Key experimental approaches:

• Pressure-pulse endurance testing: 240 cycles of rapid pressure changes to simulate harsh process conditions, monitoring spike counts and retention time shifts.
• Thermal stability assessment: Conditioning at 250 °C followed by bleed measurement to evaluate phase loss and stabilization time.
• Chromatographic performance trials: Separation of solvent mixtures, permanent gases (using a µ-TCD detector), and light hydrocarbons (using FID) to assess peak shape, resolution, and sensitivity.

Instrumentation used:

• Agilent/HP 6890 GC with FID detector for solvent and hydrocarbon analyses.
• µ-TCD detector for permanent gas separations on an MXT®-Msieve 5A column.
• Metal MXT® PLOT columns: Q-BOND (porous polymer), Msieve 5A (molecular sieve), and Alumina BOND for C1–C5 isomers.

Key Results and Discussion

• Enhanced mechanical stability: MXT®-Q-BOND columns exhibited minimal particle generation and negligible retention shifts after 240 pressure cycles, whereas competitor columns showed significant spiking and retention drift.
• Superior thermal tolerance: New bonded MXT® PLOT phases demonstrated lower bleed, leading to faster stabilization and improved sensitivity compared to conventional metal PLOT columns.
• Optimized separations:
  
  • MXT®-Q-BOND provided sharp, symmetric peaks for polar and nonpolar solvents including alcohols.
  • MXT®-Msieve 5A achieved baseline resolution of permanent gases (He, Ar, O₂, N₂, CO, CH₄) with high chromatographic efficiency.
  • MXT®-Alumina BOND/Na₂SO₄ delivered fully resolved C1–C5 hydrocarbon isomers with inert surface behavior.

Benefits and Practical Applications

• Increased uptime and reliability in continuous GC process analyzers due to reduced column maintenance.
• Improved analytical precision and reproducibility for quality assurance in petrochemical production.
• Higher sensitivity and faster cycle times support tighter process control and faster decision making.

Future Trends and Potential Applications

Further developments may include novel adsorbent materials and tailored phase chemistries to extend the range of detectable compounds. Integration with advanced detectors and automated sampling systems will enhance process analytical technology (PAT) frameworks. Emerging applications in biofuels, green chemicals, and environmental monitoring may benefit from these robust PLOT columns.

Conclusion

Restek® MXT® PLOT columns with advanced bonding technology offer a significant upgrade over conventional metal PLOT columns, delivering exceptional mechanical and thermal stability, reproducible flow behavior, and high chromatographic performance. These features make them ideally suited for demanding, continuous GC process monitoring in petrochemical and related industries.