Theory and practice of a variable dome splitter for gas chromatography-olfactometry

Area of Science:

• Analytical Chemistry
• Chemical Engineering
• Physical Chemistry

Background:

• Olfactometric measurements require splitting gas chromatography (GC) effluent between detectors and sniffing ports.
• Simple flow splitters achieve fixed ratios, while variable ratios necessitate control flows, such as in dome splitters.
• Preliminary tests showed dome splitters deviate from expected ratios due to temperature-dependent flow restrictors and internal pressure.

Purpose of the Study:

• To develop a physical model for a GC dome splitter to predict and optimize split ratios.
• To account for temperature-dependent flow restrictors and internal pressure variations.
• To ensure accurate effluent splitting across the entire GC temperature range.

Main Methods:

• Developed a physical model of the dome splitter's flow system.
• Incorporated temperature dependence of flow restrictors and internal dome pressure.
• Solved flow and mass balance equations for a compressible, isothermal, and laminar flow regime.

Main Results:

• Theoretical calculations from the model showed good agreement with experimental measurements.
• The model successfully predicted deviations from expected split ratios.
• Identified the need to consider temperature effects for accurate splitter performance.

Conclusions:

• The developed physical model accurately describes GC dome splitter behavior.
• The model can be used to optimize the design of flow restrictors.
• Enables calculation of effective split ratios at any given temperature during a GC run.