Split injection in GC — What does the term “split” specifically mean in the context of a split/splitless inlet?

Introduction / Context:
Split/splitless inlets control the amount of analyte that reaches the analytical column. Proper understanding of split mode is essential for avoiding column overload, achieving sharp peaks, and maintaining linear detector response ranges.

Given Data / Assumptions:

• In split mode, most of the vaporized sample is vented.
• Only a small, controlled fraction is transferred to the column.
• Split ratio (e.g., 50:1) defines the fraction entering the column.

Concept / Approach:
The sample is vaporized in the inlet liner; carrier gas sweeps part of the vapor out the split vent while the remainder enters the column. This prevents overload for concentrated samples and allows fast injections with good focusing at the column head.

Step-by-Step Solution:

Verification / Alternative check:
Changing the split ratio predictably scales peak areas for non-overloaded analytes; instrument logs show split vent flows during split injections.

Why Other Options Are Wrong:

• No sequential or parallel multi-port injections are implied.
• Program splitting is unrelated to inlet operation.
• Therefore, the correct concept is venting a fraction to waste.

Common Pitfalls:
Using too low a split ratio with concentrated samples causes fronting and nonlinearity; too high a ratio can push analyte below detection limits.

Final Answer:
Diverting a defined fraction of the vaporized sample to waste so only a portion enters the column.