Which of the following methods allows for the separation of charged particles based on their rates of migration in an electric field?

• A. Rheophoresis
• B. Electrophoresis
• C. Electroendosmosis
• D. Ion exchange

Answer: (B)

Charged particles move in an electric field, and how fast they migrate depends on their net charge, size, and how easily they move through the surrounding medium. Electrophoresis uses this principle by applying a voltage across a gel or capillary so differently charged or differently sized molecules travel at different speeds. The medium acts like a sieve and adds friction proportional to the particle’s size, so smaller or more highly charged molecules move faster, producing distinct bands that separate over time. This direct relationship between charge-driven force and migration rate is what makes electrophoresis the method for separating charged particles by how quickly they move in an electric field.

Electroendosmosis involves movement of the solvent itself due to the electric field and can influence results but is not the primary mechanism that separates particles by their migration rates. Ion exchange relies on chemical affinity to a charged resin rather than migration under a field. The term about rheophoresis isn’t the standard mechanism used here. So the method that best fits the description is electrophoresis.