Modern gas chromatography may require several different gases in order to operate. The nature and purity of the gas required is dictated by the type of inlet, column, and detector system used. The aims of this module include outlining the nature and quality of the gases required for GC analysis, as well as highlighting the various methods for controlling gas pressure and cleanliness including troubleshooting strategies. The use of gas generators as a viable alternative to cylinders for GC gas supply will be discussed. The principles of manual and electronic pressure control for GC carrier, inlet, and detector gas regulation are described as well as the differences between constant pressure and constant flow experiments.

At the end of this topic you will be able to recognize the gases required for carrier, inlet and detector operation, describe the required gas cleanliness and propose practical solutions for ensuring gas cleanliness requirements are met, describe which gases may be supplied by generator, illustrate various means be which gas flows are controlled and regulated, identify the two primary types of gas flow control and demonstrate that you understand the differences between them using schematic diagrams, and explain how GC analyses might differ when separations are carried out in constant flow or constant pressure mode. 

Topics include:

• Gases required for GC
• Gas supply management
• Quality of gas supply
• Gas generators - using hydrogen in the lab
• Manual pressure control
• Electronic pressure control
• Pressure/flow programming