Accelerating Single or Dual Column Environmental Methods using Low Thermal Mass Column Technology and Software-Controlled Independent Module Heating

Significance of the Topic

Environmental laboratories face increasing demand for high throughput and cost efficiency without compromising data integrity. Fast gas chromatography is essential for routine monitoring of semivolatile organics and polycyclic aromatic hydrocarbons (PAHs) in environmental samples. Implementing low thermal mass column technology and software-controlled heating modules can dramatically reduce analysis time, lower energy consumption, and boost productivity.

Objectives and Study Overview

This study demonstrates the performance enhancements achieved by retrofitting an Agilent 6890 GC coupled with a 5975 MSD using the Gerstel Modular Accelerated Column Heater (MACH) System. Two standard EPA environmental methods—Method 610 for PAHs and Method 8270 for semivolatile organics—were evaluated to quantify reductions in cycle time, assess separation quality, and confirm ease of method transfer.

Methodology and Used Instrumentation

• Gas chromatograph: Agilent 6890 GC
• Detector: Agilent 5975 Mass Selective Detector
• Heater modules: Gerstel MACH low thermal mass column modules
• Autosampler: Gerstel MPS 2
• Columns: Restek Rtx-5Sil-MS capillaries (0.18 mm i.d. × 0.18 μm and 0.25 mm i.d. × 0.25 μm) installed in toroidal modules

Key method features:

• Heating rates exceeding 1000 °C/min and cooling times as fast as 30 s
• Independent dual column heating for tailored temperature programs and two-dimensional heart-cutting
• Direct transfer of existing methods with accelerated ramp profiles

Main Results and Discussion

• EPA 610 (PAHs): Cycle time reduced by 30–50 % while maintaining comparable peak resolution, including >60 % separation of the critical benzo[b]- and benzo[k]-fluoranthene pair.
• EPA 8270 (Semivolatiles): A 76-compound subset was separated in less than half the conventional run time, preserving baseline resolution for challenging isomeric pairs (e.g. dichlorobenzenes) and high-molecular-weight PAHs.

The MACH system’s rapid temperature programming and precise control of holds and negative ramps enabled optimized separations without loss of sensitivity or precision.

Benefits and Practical Applications

• Substantial increase in sample throughput and instrument efficiency
• Retention of analytical quality—linearity, precision, and sensitivity—equivalent to conventional ovens
• Use of standard capillary columns and fittings eliminates leak concerns and prolongs column life
• Flexibility for both single-column and advanced two-dimensional workflows

Future Trends and Potential Applications

Advancements in low thermal mass technology are poised to enhance two-dimensional GC methodologies, integrate with automated multi-module platforms, and further reduce energy usage. Emerging applications include rapid forensic screening, high-throughput pharmaceutical quality control, and real-time environmental monitoring.

Conclusion

The Gerstel MACH system offers a robust, user-friendly solution for accelerating gas chromatography by combining low thermal mass heating with software-controlled modules. Retrofitting existing GC-MS instruments can halve analysis times for standard environmental methods, effectively doubling throughput while maintaining data integrity.

References

[1] C Leonard A Grall R Sacks Anal Chem 1999 71 2123
[2] G L Reed K Clark Baker H M McNair J Chromatogr Sci 1999 22 300