What is the purpose of loading dye in electrophoresis?

Loading dye is primarily used in electrophoresis to increase the density of a sample, allowing it to better settle into the wells of the gel. This is important because when samples are placed into the wells for electrophoresis, a higher density loading dye ensures that the sample remains where it is deposited rather than floating away or mixing with the buffer.

The loading dye also typically contains tracking dyes that help visualize the progress of the electrophoresis during the run, making it easier to determine when to stop the process. The mixture of the loading dye often has a heavier weight compared to the sample buffer, ensuring it sinks effectively.

The other options mentioned do not fully capture the primary function of loading dye: determining pH, controlling temperature, or enhancing separation are not direct roles that loading dye plays during the electrophoresis process.