Which statement does not apply to gas-liquid chromatography?

Which statement does not apply to gas-liquid chromatography?

• A. Separation depends on volatility of the sample.
• B. Separation depends on the sample's solubility in the liquid layer of the stationary phase.
• C. Stationary phase is a liquid layer adsorbed on the column packing.
• D. Mobile phase is a liquid pumped through the column.

Answer: (D)

Gas-liquid chromatography separates compounds by partitioning them between a mobile gas and a liquid stationary phase coated on the column. Each analyte’s tendency to stay in the liquid stationary phase versus the moving gas determines how long it is retained, so volatility and affinity for the stationary phase shape the elution order. More volatile components tend to spend more time in the mobile gas and elute earlier, while substances with greater solubility in the liquid stationary phase are retained longer.

The stationary phase in this method is indeed a liquid film on the column packing (or on the capillary wall), which is what drives the partitioning behavior. The mobile phase is not a liquid; it is an inert carrier gas (like helium, nitrogen, or hydrogen) pushed through the column.

Therefore, the statement about the mobile phase being a liquid pumped through the column does not apply to gas-liquid chromatography.