capillary electrophoresis
/ KAP-ih-lair-ee ih-lek-troh-fuh-REE-sis /
Picture a tug-of-war along a very thin glass straw filled with salt water. Apply a high voltage across the straw, and charged molecules feel a steady pull toward one end; lighter, more highly charged ones surge ahead while heavier or less charged ones lag. Capillary electrophoresis is exactly this race, run inside a hair-thin tube under a strong electric field.
Formally, capillary electrophoresis separates charged species inside a narrow fused-silica capillary filled with an electrolyte solution, by applying a high voltage along its length. Each ion migrates at a speed set by its charge-to-size ratio; a bulk flow of the solution, driven by the charged capillary wall, often carries everything toward the detector at the far end. Components reach the detector in an order set by their net mobility.
It matters because the thin capillary dissipates heat well, allowing very high voltages and therefore extremely sharp, fast separations of tiny sample amounts — ideal for proteins, DNA fragments, ions, and chiral drugs. Its honest limits are sensitivity and robustness: the minuscule sample and short optical path make detection challenging, and migration times can drift if the capillary wall or buffer condition changes.
A forensic lab loads a few nanolitres of digested DNA into a capillary, applies a high voltage, and watches the fragments separate by size as they migrate, building the electropherogram that becomes a DNA fingerprint.
A high voltage races charged molecules through a hair-thin tube, sorting them by mobility.
Capillary electrophoresis is a cousin of slab-gel electrophoresis but uses a tiny tube and a strong field, trading the gel's parallel lanes for one fast, automated channel.