What is column chromatography primarily used for?

Column chromatography is primarily used as a method for separating molecules based on their interactions with a stationary phase and their solubility in a mobile phase. This technique involves packing a column with a stationary phase material, and when a mixture is introduced, different components of the mixture will interact with the stationary phase to varying degrees. As a result, they travel through the column at different rates, leading to their separation.

The correct answer highlights that column chromatography relies on gravity and molecular interaction within a vertical chamber, which effectively conveys the fundamental principles of the technique. The separation process is influenced by the chemical properties of the molecules, such as polarity or size, enabling the separation of complex mixtures into individual components.

The other options, while they describe important techniques and methods used in biochemistry or molecular biology, do not accurately represent the primary function of column chromatography. Analyzing protein sequences typically involves techniques like mass spectrometry or Edman degradation. Separating molecules based on size and charge may refer more specifically to gel electrophoresis rather than column chromatography. Visualizing DNA fragments is primarily achieved through techniques like agarose gel electrophoresis or Southern blotting.