Analytical chemistry — gas chromatography In gas chromatography of volatile mixtures, components are separated primarily due to differences in which property?

Introduction / Context:
Gas chromatography (GC) separates volatile analytes as they partition between a mobile gas phase (carrier gas) and a stationary phase (often a liquid film on capillary walls). Understanding the controlling physicochemical parameter explains retention and resolution.

Given Data / Assumptions:

• Analytes are volatile or made volatile.
• Columns contain a stationary phase with which analytes interact.
• Carrier gas flow transports analytes through the column.

Concept / Approach:
The central parameter in GC is the distribution (partition) coefficient, K, which reflects the tendency of a compound to spend time in the stationary phase versus the mobile phase. Higher affinity for the stationary phase increases retention time; lower affinity elutes earlier.

Step-by-Step Solution:
Model elution as repeated partitioning events between phases.Relate retention time to partition coefficient: greater interaction → longer retention.Choose the option explicitly invoking partition coefficients.

Verification / Alternative check:
Temperature programming alters partition coefficients by changing analyte vapor pressures and interaction strengths, confirming that partitioning governs separation.

Why Other Options Are Wrong:
Conductivity (option b) is not the GC separation principle.Molecular weight (option c) can correlate with retention but is not the fundamental basis.Molarity of injection (option d) influences peak shape/overload, not intrinsic separation.

Common Pitfalls:
Assuming GC is size-exclusion or purely mass-based; neglecting temperature effects on partitioning.

Final Answer:
Partition coefficients between the mobile gas and stationary liquid/solid phase.