Which buffer is used for acidic conditions in electrophoresis?

• A. Tris buffer
• B. Citrate buffer
• C. Barbital buffer
• D. Glycine buffer

Answer: (B)

In electrophoresis, keeping the pH stable is crucial because the charge on molecules and their movement depend on the surroundings. For acidic conditions, you want a buffer that maintains a low pH despite small amounts of base that may be introduced during the run. Citrate fits this role well because it’s a polyprotic acid with pKa values around 3.1, 4.8, and 6.4. Those pKa values provide buffering capacity across the acidic to near-neutral range, helping the medium stay acidic throughout the separation.

Other common buffers have higher buffering ranges (for example, Tris has a pKa around 8.1 and buffers best in the basic region; barbital and glycine systems are typically used at near-neutral to basic pH). They don’t maintain an acidic environment as effectively as citrate does, which is why citrate buffer is the preferred choice for acidic conditions in electrophoresis.