The CTO-20A is a forced air-circulation-type column oven. It can regulate the temperature in a range going from 10 deg. C above room temperature to 85 deg. C. The CTO-20AC, using an electronic cooler, can regulate the temperature in a large range going from 10 deg. C below room temperature to 85 deg. C. In addition to the column, various other parts and units can be accommodated, including a manual injector, gradient mixer, high-pressure flow-line selection valves, a conductivity-detection cell block, and a reaction coil.