Which of the following statements best describes electrophoresis?

• A. Electrophoresis separates charged particles based on their rates of migration in an electric field
• B. Electrophoresis separates molecules solely by size
• C. Electrophoresis uses magnetic fields to separate analytes
• D. Electrophoresis measures pH directly

Answer: (A)

Electrophoresis works by using an electric field to move charged molecules through a gel or buffer. Molecules with net charge migrate toward the electrode of opposite charge, and their speed—the rate of migration—depends on how strongly they are charged and how much friction they experience in the medium. Smaller or more highly charged particles travel faster, while larger or less charged ones move more slowly, leading to separation over time. This description captures the essential mechanism: separation occurs because charged particles migrate at different rates in the electric field. It wouldn’t be correct to describe electrophoresis as separating solely by size, since charge influences movement; it doesn’t rely on magnetic fields; and it doesn’t measure pH directly.