Abstract: Capillary column oxidation in gas chromatography systems, particularly of polyimide clad columns, is a major cause of column failure and it limits the maximum temperature at which columns can be used. A gas chromatography column oven system is described which utilizes inert gas to substantially eliminate column oxidation thereby increasing column thermal stability. These column oven systems thus increase column lifetime and maximum operating temperature. The column oven systems comprise pneumatically sealed oven enclosures with sealed access ports, sealed sample line ports, and inlet and outlet gas ports to which are connected an inert gas supply and an exhaust gas control system respectively.

Abstract: A microwave heating apparatus is used for heating a chromatographic column assembly containing a microwave absorbing material. The microwave heating apparatus includes an antenna transmitting a microwave signal and a resonant cavity containing the chromatographic column assembly. The chromatographic column assembly extends relative to predetermined electromagnetic field strength contours within the resonant cavity to provide a predetermined heating profile along the length of the chromatographic column assembly. For example, a single-mode chromatographic column microwave oven can be used to heat a coiled chromatography column to a desired temperature gradient along its length. Oven design embodiments utilizing coaxial transmission line structures, coaxial resonators, and cylindrical resonators are described. Oven designs are provided to achieve more suitable oven size for fixed operating frequencies. Apparatuses for impedance matching an oven to a microwave source are described.

Abstract: A microwave heating apparatus is used for heating a chromatographic column assembly containing a microwave absorbing material. The microwave heating apparatus includes an antenna transmitting a microwave signal and a resonant cavity containing the chromatographic column assembly and the antenna. The chromatographic column assembly extends relative to predetermined electromagnetic field strength contours within the resonant cavity to provide a predetermined heating profile along the length of the chromatographic column assembly. For example, a single-mode chromatographic column microwave oven can be used to heat a coiled chromatography column to a desired temperature gradient along its length. Oven design embodiments utilizing coaxial transmission line structures, coaxial resonators, and cylindrical resonators are described. To control the electromagnetic field gradient in the axial direction, the oven designs provide for varying some part of the oven geometry in the axial direction.

Abstract: A microwave heating apparatus is used for heating a chromatographic column assembly containing a microwave absorbing material. The microwave heating apparatus includes an antenna transmitting a microwave signal and a resonant cavity containing the chromatographic column assembly and the antenna. The chromatographic column assembly extends relative to predetermined electromagnetic field strength contours within the resonant cavity to provide a predetermined heating profile along the length of the chromatographic column assembly. For example, a single-mode chromatographic column microwave oven can be used to heat a coiled chromatography column to a desired temperature gradient along its length. Oven design embodiments utilizing coaxial transmission line structures, coaxial resonators, and cylindrical resonators are described. To control the electromagnetic field gradient in the axial direction, the oven designs provide for varying some part of the oven geometry in the axial direction.

Abstract: A chromatography column for microwave heating either incorporates microwave absorbing material into the column itself or positions the column adjacent to microwave absorbing material so that the column and the chromatography sample contained therein are heated by the microwave absorbing material via conduction or convection. For example, a microwave absorbing material (e.g., ferrite) can be fused into the inner silica layer or incorporated in an outer polymer layer of the column. Microwave absorbing material can also be incorporated into an external element (e.g., an outer tube, sleeve, or spool) positioned adjacent to the chromatography column. A layer of thermal insulation can be placed around the column to decrease the rate of heat loss. Optionally, a gap can be provided between the chromatography column and thermal insulation to further reduce heat loss during the heating cycle and to accelerate cooling at the end of the heating cycle by making it possible to ventilate the heated column.

Abstract: A chromatography column for microwave heating either incorporates microwave absorbing material into the column itself or positions the column adjacent to microwave absorbing material so that the column and the chromatography sample contained therein are heated by the microwave absorbing material via conduction or convection. For example, a microwave absorbing material (e.g., ferrite) can be fused into the inner silica layer or incorporated in an outer polymer layer of the column. Microwave absorbing material can also be incorporated into an external element (e.g., an outer tube, sleeve, or spool) positioned adjacent to the chromatography column. A layer of thermal insulation can be placed around the column to decrease the rate of heat loss. Optionally, a gap can be provided between the chromatography column and thermal insulation to further reduce heat loss during the heating cycle and to accelerate cooling at the end of the heating cycle by making it possible to ventilate the heated column.