Headspace GC — What is the primary purpose of headspace analysis in gas chromatography?

Introduction / Context:
Headspace sampling is a widely used GC technique for matrices that contain volatile analytes but are themselves complex or non-injectable (e.g., solids, viscous liquids, biological fluids). Understanding what headspace measures is essential for correct sample prep and calibration.

Given Data / Assumptions:

• The analyte of interest must partition into the gas phase above the sample (the headspace).
• Non-volatile matrix components are left behind and do not enter the column.
• Automated static or dynamic (purge-and-trap) headspace systems are common.

Concept / Approach:
Headspace analysis quantifies volatile or semi-volatile compounds that equilibrate between the sample and the gas phase in a sealed vial at controlled temperature. An aliquot of the headspace gas is introduced to the GC, minimizing matrix effects and protecting the column from non-volatile contaminants.

Step-by-Step Solution:

Verification / Alternative check:
EPA and pharmacopoeial methods specify headspace GC for residual solvents and VOCs, demonstrating suitability for volatile analytes from diverse matrices.

Why Other Options Are Wrong:

• Psychological state: not analytical chemistry.
• Column contents ahead of the sample: unrelated concept.
• Non-volatiles cannot be assayed directly by headspace.
• Headspace is not restricted to neat solvents; matrices are diverse.

Common Pitfalls:
Expecting headspace to capture non-volatiles; those require derivatization or liquid injection techniques.

Final Answer:
Analyse volatile compounds released from solid or liquid samples.