Quasi-adiabatic vacuum-based column housing for very high-pressure liquid chromatography

• A prototype vacuum-based housing was built to insulate a chromatographic column.
• The distance between the outer column wall and the inner oven wall is 2.7 cm.
• Below 10−4 Torr vacuum air pressure heat transfer is only governed by surface radiation.
• The adiabaticity of the housing was measured from the balance in eluent enthalpy.
• Less than 1% of viscous heat is lost by radiation to the external environment.

A prototype vacuum-based (10−6 Torr) column housing was built to thermally isolate the chromatographic column from the external air environment. The heat transfer mechanism is solely controlled by surface radiation, which was minimized by wrapping the column with low-emissivity aluminum tape. The adiabaticity of the column housing was quantitatively assessed from the measurement of the operational pressure and fluid temperature at the outlet of a 2.1 mm × 100 mm column (sub-2 μm particles). The pressure drop along the column was raised up to 1 kbar. The enthalpy balance of the eluent (water, acetonitrile, and one water/acetonitrile mixture, 70/30, v/v) showed that less than 1% of the viscous heat generated by friction of the fluid against the packed bed was lost to the external air environment. Such a vacuum-based column oven minimizes the amplitude of the radial temperature gradients across the column diameter and maximizes its resolving power.