GC 6-Port Sampling Valve – Fundamentals

The 6-port sampling valve is the most common injection device used in process gas chromatographs. It operates in two fixed positions: LOAD (PURGE) and INJECT. Correct valve sequencing is critical for repeatable chromatography.

6-Port Valve – LOAD vs INJECT Operation

During LOAD, the sample continuously refreshes the loop and vents. During INJECT, the valve rotor switches and carrier gas pushes the loop contents into the GC column.

Key Points for Technicians

• Only two valid valve positions exist: LOAD and INJECT.
• During LOAD, the GC column is isolated from the sample.
• During INJECT, carrier gas pushes the loop contents into the column.
• Incorrect timing causes missing or distorted peaks.
• Most “no peak” alarms are related to valve actuation or air supply.