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The GC oven

  • Page ID
    61155
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    The oven is a fundamental component of the GC system. The oven temperature must be controlled very accurately over a wide range of temperatures to assure accurate isothermal temperature settings and temperature programming.

    Requirements for a GC oven:

    • Temperature range: 5 - 450oC
    • Temperature stability: about 0.1 degrees
    • Programming rate: 0.1 - 50oC/minute
    • Reproducability: < 1%
    • Cooldown time: 350 to 50oC in less than 10 minutes

    Separation usually occurs at a higher temperature than the ambient temperature of about 25°C. The temperature during an analysis should be high enough to evaporate the sample components.

    The most important role of the oven temperature is its effect on the partition coefficient of the analytes between stationary and mobile phase. An increase in temperature will result in decreased retention of analytes and vice versa.

    Since temperature is such an important parameter, there is a high demand on the stability and reproducibility of temperature settings.

    Isothermal Analysis and Temperature Programming

    If a sample contains components with closely similar boiling points, adequate separation with a short analysis time is obtained at one specific oven temperature. This is called an isothermal analysis.

    Isothermal vs Temperature Gradient

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    In the bottom experiment the temperature is programmed to increase in time and the compounds with higher boiling temperature show elute faster and show higher peaks.

    The optimum column temperature is dependent upon the boiling point of the sample components.

    When the sample components have a wide range of boiling points, efficient separation within a short analysis time is not to be expected. Temperature-programmed analysis is preferred for such samples. Temperature programming ensures complete and efficient (sharp peaks) separation of early as well as late-eluting analytes within resonable analysis times.

    A temperature program generally consists of a series of isothermal and temperature rise steps. Three variables play an important role in temperature programming:

    • the initial temperature should be such that the most volatile components are adequately separated . This temperature is generally well below the boiling point of the lowest boiling component.
    • the final temperature should be such that the highest boiling components should leave the column properly separated. This temperature is generally near the boiling point of the highest boiling component present in the sample.
    • the temperature rate: The temperature rise profile can be linear, multi-linear, convex and concave.

    Linear Temperature Program

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    The GC oven is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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