Gas Chromatography: Columns, Temperature Programming and Detectors · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Heat as a separation knob

Science · Chemistry · ages 19-20
Name ______________________   Date ____________

  1. Which component makes the first peak in a chromatogram?

    • The heaviest one
    • The one sticking least to the stationary phase
    • The most polar one

  2. What is the mobile phase in gas chromatography?

    • An inert carrier gas such as helium
    • A polar liquid solvent
    • The column coating itself

  3. Raising the column temperature makes heavy sticky components let go sooner.

    Circle one:   True   False

  4. A sample contains a nonvolatile salt. How can it still run on a GC?

    • Inject more of it
    • Derivatise it into a volatile form
    • Cool the column below freezing

  5. What goes wrong in an isothermal run of a wide boiling mixture?

    • Early peaks crowd while late ones broaden and drag
    • All peaks vanish completely
    • The carrier gas turns liquid

  6. Why must the injected sample be tiny?

    • Large samples explode
    • Too much sample overloads the phase and smears the bands
    • The detector counts only small numbers

  7. A destructive detector still lets you collect the sample afterwards.

    Circle one:   True   False

  8. A chromatogram shows broad overlapping peaks after a large injection, though the method worked before. What is the diagnosis?

    • Carrier gas that is too pure
    • Peaks that elute too early
    • Column overload from too much sample
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Heat as a separation knob W1-mt_C70HPdO2Dk-s1

  1. The one sticking least to the stationary phase · Weak stickers hurry through while strong ones lag.
  2. An inert carrier gas such as helium · A gas must carry the vapour through the coated column.
  3. True · Heat shakes molecules off the coating and back into the gas.
  4. Derivatise it into a volatile form · Derivatisation caps sticky groups and makes the molecule volatile.
  5. Early peaks crowd while late ones broaden and drag · One fixed heat cannot suit both light and heavy components.
  6. Too much sample overloads the phase and smears the bands · Overload floods the coating so bands broaden and overlap.
  7. False · Destructive detection consumes the sample to sense it.
  8. Column overload from too much sample · Same method plus bigger injection plus smeared peaks spells overload.
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