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

Heat as a separation knob

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

  1. Two compounds have similar volatility at the run temperature. Under the same GC conditions, which generally elutes earlier?

    • The one interacting more with the phase
    • The one interacting less with the phase
    • Both must leave at exactly the same time

  2. What serves as the mobile phase in GC?

    • A flowing carrier gas, such as helium
    • A flowing liquid mixture, such as water
    • A fixed stationary film, such as a polymer

  3. A GC temperature programme can start cooler to retain early compounds, then raise the temperature to reduce late retention.

    Circle one:   True   False

  4. A hydroxyl-containing analyte has poor GC volatility. A proposed derivative may improve it. Which plan is justified before relying on the derivative method?

    • Check derivative formation, stability and response
    • Use the starting compound's calibration without retesting
    • Assign every new peak to the derivative without a check

  5. A low isothermal temperature resolves early compounds but leaves late compounds very delayed. Which trial addresses this trade-off?

    • Raise the sample mass but keep the oven fixed
    • Keep the low oven temperature for a longer run
    • Raise the oven temperature later in the run

  6. You need sensitive detection of trace organic compounds and do not need sample recovery. Which comparison supports choosing FID rather than TCD?

    • TCD is usually more sensitive for these organic traces
    • FID is usually more sensitive for these organic traces
    • Both detectors have identical responses to all organic traces

  7. With no flow split before an FID, unchanged analyte can be collected after it passes through the detector.

    Circle one:   True   False

  8. A concentrated GC sample gives fronting peaks. Dilution restores their shape at the same injection volume and settings. Which explanation is best supported?

    • An injector leak proved by peak shape alone
    • A permanent detector fault independent of mass
    • Sample-mass overload in the concentrated run
LightMySky · lightmysky.comW1-mt_C70HPdO2Dk-s1

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 interacting less with the phase · With comparable volatility, weaker stationary-phase interaction generally gives lower retention.
  2. A flowing carrier gas, such as helium · The carrier gas is the moving phase; the column film is stationary.
  3. True · Programming can help a broad volatility range, but successful separation still needs checking.
  4. Check derivative formation, stability and response · A useful derivative must form, survive the conditions and give a characterised response. A new peak or old calibration does not establish those facts.
  5. Raise the oven temperature later in the run · A later temperature rise can reduce late retention while retaining the useful cooler start.
  6. FID is usually more sensitive for these organic traces · FID is generally more sensitive for many organic traces. Its destructive operation is acceptable for this stated task.
  7. False · FID consumes the material entering its flame. A pre-detector split could reserve material, but the question excludes it.
  8. Sample-mass overload in the concentrated run · Reducing sample mass improved shape while volume and settings stayed fixed. That supports overload, not proof of a leak.
Worksheet · LightMySky