A high pressure liquid chromatography jacket includes a rectangular, fluid-tight enclosure which has a removable cover on which a pair of tubing seal fittings are mounted. The fittings form a fluid-tight seal around the inlet and discharge tubes of a chromatographic column which is mounted in the enclosure. The enclosure is connected to a source of temperature controlled fluid which circulates through the enclosure and controls the temperature of the chromatographic column.In an alternative embodiment of the invention, a valve is provided which allows sample materials being loaded to enter a sample storage loop, which is exposed to the temperature controlled fluid. The sample, whose temperature has been controlled by the temperature controlled fluid, is then injected into a chromatographic column under high pressure.