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)

In gas-liquid chromatography, separation relies on partitioning of analytes between a mobile phase that is a gas and a liquid stationary phase coated onto the column. The extent of retention for a compound is governed by its volatility—how readily it moves into the gas phase—and its solubility in the liquid stationary phase, which makes it spend more time drawn out in the column. The stationary phase being a liquid layer adsorbed on the column packing is accurate, providing the medium for this partitioning. The mobile phase, however, is not a liquid pumped through the column; it is a carrier gas (such as helium or nitrogen) that drives the flow. So the statement about the mobile phase being a liquid does not apply.