Diafiltration is defined as which?

• A. A filtering process by which some molecules in a sample move out of a solution as it passes by a membrane
• B. A chromatography method
• C. A method to observe pigments
• D. A method to measure pH

Answer: (A)

Diafiltration is a membrane-based separation that uses a semipermeable barrier to move small molecules and solvent out of the solution while larger molecules are retained. As the sample passes by or through the membrane, small solutes can diffuse or flow through the pores, effectively washing them away, which is why the process is described as a filtering step where some components leave the solution. This makes diafiltration useful for buffer exchange or desalting around larger solutes like proteins without losing the larger molecules themselves. It’s not chromatography, which separates mainly through interactions with a stationary phase, not observation of pigments, and not a method for measuring pH.