Extending analyte boiling point range using thinner film porous layer open tubular columns paired with GC×GC-MS

Significance of the Topic

Extending the boiling point range of analytes in gas chromatography addresses critical needs in environmental monitoring, petrochemical analysis, and process control by enabling accurate quantification from ultralight gases to semi-volatile organics.

Objectives and Overview of the Study

This work explores the use of thinner film porous layer open tubular (PLOT) columns in GC×GC coupled with mass spectrometry to enhance resolution, expand temperature limits, and improve detection of low-boiling and semi-volatile compounds. The study benchmarks thinner PLOT columns against conventional wall coated open tubular (WCOT) columns and evaluates performance with calibration and refinery mixes.

Methodology

Analyses were performed using GC×GC-qMS with autosampler and a custom high-temperature diaphragm valve for sample loops. The first dimension employed PLOT-S columns of various film thicknesses (8 µm, 4 µm, 2 µm) at 30 m length and 0.25 mm inner diameter, flowing at 1.4 mL/min. The second dimension used Rtx-200 WCOT columns (5 m × 150 µm × 2 µm) at 2.0 mL/min. Temperature programs ranged from 30 °C or 100 °C ramped at 5–15 °C/min to 250 °C. Calibration mixes (75 components) and refinery samples (27 components) were analyzed with split injections, and mass channels spanned m/z 40–334.

Instrumentation Used

• GC×GC system with qMS detector
• Custom high-temperature diaphragm valve (up to 325 °C) with Kalrez seals
• PLOT-S columns (8 µm, 4 µm, 2 µm) and Rtx-200 WCOT columns
• Auto-injector with 10 mL sample loop

Main Results and Discussion

Thinner PLOT films significantly enhanced the detection of ultralight (methane, ethane) and semi-volatile compounds (nitrobenzene, naphthalene). The 2 µm films provided sharper peaks and better separation of refinery mix up to n-hexadecane compared with thicker films. Reduction in film thickness reduced retention times and improved modulation efficiency in GC×GC, demonstrating compatibility with rapid second-dimension analysis.

Benefits and Practical Applications

The optimized thinner PLOT columns extend analyte scope without sacrificing resolution, enabling comprehensive profiling of complex mixtures such as natural gas, gasoline, and petrochemical streams. Enhanced selectivity and sensitivity support environmental assays, quality control in refineries, and process monitoring.

Future Trends and Opportunities

Further research will focus on shortening column length to increase throughput, exploring multi-dimensional valve designs, and validating retention time reproducibility across diverse matrices. Integration with advanced data analysis and machine learning will further expand application domains.

Conclusion

Thinner film PLOT columns in GC×GC-qMS provide a robust approach for broad-range analyte separation, improving detection from light gases to semi-volatile organics. This advancement opens new avenues in chromatographic science and industrial analytics.

References

• Mikaliunaite L.; Bell D. S.; Synovec R. E. Extending analyte boiling point range using thinner film porous layer open tubular columns paired with GC×GC-MS. LCGC North America 2022, 35, 388–394.
• Mikaliunaite L.; Sudol P. E.; Cain C. N.; Synovec R. E. Application of PLOT columns for light compounds in gas mixtures. J. Chromatogr. A 2021, 1652, 462358.
• Mikaliunaite L.; Trinklein T. J.; Ochoa G. S.; Sudol P. E.; Bell D. S.; Synovec R. E. Next generation PLOT-based GC×GC using qMS for added selectivity: ultralight to semi-volatile compounds. J. Chromatogr. O 2023, 3, 100076.