HPLC Column Oven The column oven controls the column temperature and, as the retention of all solutes is determined by the magnitude of the distribution coefficient of each solute between the two phases, which is, in turn, controlled by the column temperature, the column oven plays an important part in controlling both the quality and analysis time of the chromatographic separation. In gas chromatography, the mobile phase entering the column is a gas of low specific heat and, thus, the heating medium can also have a relatively low specific heat and, consequently, an air circulating oven is satisfactory. An air oven is even satisfactory when employing relatively fast temperature programming. In liquid chromatography, however, the mobile phase entering the system has a relatively high specific heat and a simple air oven is rarely satisfactory. Using a liquid as the thermostatting medium is thermally satisfactory but makes column changing difficult and unpleasant and the medium needs to be continuously topped up. Various methods have been adopted to simplify the liquid chromatography column oven and one of the more satisfactory is to employ a mobile phase pre-heater in conjunction with a circulating air oven. The mobile phase is preheated by passing it through a heat exchanger. One type of efficient heat exchanger that has been successfully employed for this purpose is the serpentine tube heat exchanger clamped to a heated block. The serpentine heat exchanger rapidly brings the mobile phase up to the temperature of the block which is set to be the same as (or slightly greater than) the oven temperature.