Which statement about the mobile phase is correct?

Which statement about the mobile phase is correct?

• A. The phase that interacts with compounds and causes separation.
• B. The phase that stays fixed in the apparatus.
• C. The phase that moves compounds through the stationary phase.
• D. The solid support that holds the sample.

Answer: (C)

The moving fluid is what drives separation in chromatography. The mobile phase is the liquid (in liquid chromatography) or gas (in gas chromatography) that travels through the column, carrying the sample components with it. As these components move, they interact with the stationary phase that lines the column. Some compounds spend more time interacting with the stationary phase, so they travel more slowly; others interact less and elute faster. This differential movement creates separation. In this light, the statement that the mobile phase moves compounds through the stationary phase is the most accurate description. It captures both that the phase is moving and that it carries analytes through the region where separation occurs. The other ideas describe related aspects but aren’t as precise: the phase that stays fixed is the stationary phase, not the mobile phase. The solid support that holds the sample is part of the stationary phase setup, not the moving phase. And while the mobile phase does influence separation through its interaction with the analytes, the core definition centers on the mobile phase being the moving solvent that carries components through the stationary phase.

The moving fluid is what drives separation in chromatography. The mobile phase is the liquid (in liquid chromatography) or gas (in gas chromatography) that travels through the column, carrying the sample components with it. As these components move, they interact with the stationary phase that lines the column. Some compounds spend more time interacting with the stationary phase, so they travel more slowly; others interact less and elute faster. This differential movement creates separation.

In this light, the statement that the mobile phase moves compounds through the stationary phase is the most accurate description. It captures both that the phase is moving and that it carries analytes through the region where separation occurs.

The other ideas describe related aspects but aren’t as precise: the phase that stays fixed is the stationary phase, not the mobile phase. The solid support that holds the sample is part of the stationary phase setup, not the moving phase. And while the mobile phase does influence separation through its interaction with the analytes, the core definition centers on the mobile phase being the moving solvent that carries components through the stationary phase.