The invention relates to a method, to a device, and to the use of a method for the gas-chromatic separation and determination of volatile substances in a carrier gas by means of a chromatographic separating capillary (1), wherein the separating capillary and/or an enveloping capillary (2) surrounding the separating capillary (1) is electrically conductive and is heated with current in the form of a resistance heater and is cooled by a forced convective flow by means of a fluid in the form of a gradient flow field in such a way that a continuous temperature gradient arises over the length of the separating capillary.

A system and method of reducing chromatographic band broadening within a separation column include passing a mobile phase through a length of a separation column, and generating a spatial thermal gradient external to and along the length of the separation column. The spatial thermal gradient is specifically configured to counteract a particular change in a property of the mobile phase as the mobile phase passes through the separation column. For example, the particular change counteracted may be a change in density or in temperature of the mobile phase. For analytical-scale columns, for example, the spatial thermal gradient may be configured to produce temperatures external to and along the length of the separation column that substantially matches temperatures predicted to form in the mobile phase along the column length as the mobile phase passes through the separation column, thereby substantially preventing formation of a radial thermal gradient in the mobile phase.

Certain configurations described herein are directed to gas chromatography devices. In some instances, the gas chromatography devices may comprise at least one heating device which can be moved along a chromatography column to provide a thermal gradient to the chromatography column. In other instances, the gas chromatography devices may comprise a heating device that can receive a moving chromatography column to provide a thermal gradient to the chromatography column. The gas chromatography devices may be configured as portable devices which can be used to perform remote analyzes.

Exemplary embodiments may compensate for expected frictional heating or Joule-Thomson cooling in chromatography columns. Frictional heating or Joule Thomson cooling are the same thing for a fluid decompressing along a porous material. Either heat is absorbed from or released to the external environment. The exemplary embodiments may cool the mobile phase to a sub-ambient temperature before the mobile phase passes through a chromatography column to compensate for the frictional heating or heat the mobile phase to a super-ambient temperature to compensate for Joule-Thomson cooling. The amount of temperature increase expected from the frictional heating or the amount of temperature decrease expected from the Joule-Thomson cooling may be calculated or estimated. Based on the amount of temperature increase or decrease expected, the set point for the heater/cooler may be determined and applied to the mobile phase. The analyte may be injected solely into a central portion of the chromatography column to further compensate for thermal gradients.

Analytical-scale separation column assemblies include a tube with a bore packed with a stationary phase through which a mobile phase flows. In one embodiment, thermal elements are disposed remotely from and unattached to the tube. The thermal elements are in thermal communication with an external surface of the tube for producing a spatial thermal gradient outside of and along a length of the tube. In another embodiment, discrete, spatially separated strips of thermally conductive material are disposed on and wrapped around an external surface of the tube. Thermal elements are disposed remotely from the tube. Each thermal element is in thermal communication with one strip of thermally conductive material by a heat-transfer device. The thermal elements produce a spatial thermal gradient outside of and along a tube length by controlling temperature of each strip of thermally conductive material disposed on and wrapped around the external surface of the tube.

A system for performing gas chromatography analyses in accordance with the present disclosure includes an analytical column and a column oven. The analytical column has an inlet portion coupled to an injector for receiving a material sample and an outlet portion coupled to a detector. The analytical column is adapted to direct the material sample from the injector to the detector. The column oven is adapted to heat the analytical column for separating constituent components of the material sample for detection by the detector.

Methods for focusing analyte peaks in liquid chromatography using a spatial temperature gradient are provided. Also provided are methods for focusing analyte peaks and improving resolution using a trap column upstream of a separation column. Further, methods are provided in which the trap column placed upstream of the separation column is packed with a temperature-sensitive polymer/copolymer, and a spatial temperature gradient is applied along the trap column for obtaining improved retentivity by trap column stationary phase, and overall improved resolution of analyte peaks.

A method of performing a chromatographic separation includes generating a spatial temperature gradient along a length of a chromatographic column in a liquid chromatography system. A sample is injected into a flow of a mobile phase to the column and a flow of a mobile phase having a composition gradient is provided to the column after the sample is received at the column. The spatial temperature gradient is moved along the length of the column from the column inlet to the column outlet during the time that the composition gradient traverses the column. This coordination of the composition gradient with the movement of the spatial thermal gradient yields a significant increase in peak capacity per unit time compared with conventional separation techniques performed in a conventional isothermal column environment.

A system for performing gas chromatography analyzes in accordance with the present disclosure includes an analytical column and a column oven. The analytical column has an inlet portion coupled to an injector for receiving a material sample and an outlet portion coupled to a detector. The analytical column is adapted to direct the material sample from the injector to the detector. The column oven is adapted to heat the analytical column for separating constituent components of the material sample for detection by the detector.

The exemplary embodiments may determine a temperature set point for an outlet heater or cooler based on available information without requiring user input or requiring only minimal user input. The exemplary embodiments may estimate the temperature set point of the outlet heater based on available information, such as pressure delta along the column, temperature at the inlet of the chromatography column, and volumetric flow rate. In some instances, the estimate may be normalized for column dimensions, such as length and diameter. Tailing factor may also be used in determining the estimate. The estimate is not computationally burdensome and can be recalculated as the chromatography column is in use.