Hyphenated Techniques: GC-MS, LC-MS and Tandem Fragmentation · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Separating first, weighing second

Science · Chemistry · ages 20-22
Name ______________________   Date ____________

  1. In chromatography, what do exit time and peak size each tell you?

    • Exit time marks the component and peak size measures its amount
    • Exit time measures the amount and peak size marks the colour
    • Both mark the temperature of the column

  2. What is a hyphenated technique such as GC-MS?

    • A separation instrument joined to a mass spectrometer
    • Two mass spectrometers glued side by side
    • A microscope joined to a telescope

  3. Gas chromatography suits volatile compounds, while liquid chromatography handles fragile and polar ones.

    Circle one:   True   False

  4. A trace peak hides under a giant one. Which view reveals it?

    • The extracted ion view for the trace mass, which shows one mass only
    • The total ion view, which shows everything at once
    • No view can ever reveal a hidden peak

  5. What must the interface between the chromatograph and the spectrometer do?

    • Destroy every molecule before it reaches the vacuum
    • Strip away the flow and deliver intact neutral molecules into the vacuum
    • Pump extra liquid into the vacuum to keep it wet

  6. What happens in a tandem MS/MS experiment?

    • Two samples are weighed on two balances at once
    • One precursor ion is picked, broken apart, and its fragments are scanned
    • The same ion is weighed twice to double check the scale

  7. A pesticide must be measured in a food extract full of matrix peaks. Why does the matrix stop interfering?

    • Food extracts never contain interfering compounds
    • Matrix peaks are always smaller than pesticide peaks
    • Two independent filters guard the result: retention time plus a characteristic transition

  8. Why does selected reaction monitoring give such low detection limits in a messy food extract?

    • It watches only chosen precursor to fragment transitions, so noise is rejected
    • It amplifies every signal including the noise
    • It removes the chromatography step to save time
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Answer key

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

Separating first, weighing second W1-mt_wmKqp8HyTL-s1

  1. Exit time marks the component and peak size measures its amount · Retention behaviour identifies, while peak area quantifies.
  2. A separation instrument joined to a mass spectrometer · Every peak in the chromatogram immediately yields its own mass spectrum.
  3. True · The method must fit the molecule, and each needs its own interface to the vacuum.
  4. The extracted ion view for the trace mass, which shows one mass only · Filtering to one mass drops the giant neighbour out of the picture.
  5. Strip away the flow and deliver intact neutral molecules into the vacuum · The vacuum instrument needs bare molecules, not the carrier flow around them.
  6. One precursor ion is picked, broken apart, and its fragments are scanned · The precursor to product pattern confirms identity even in dirty samples.
  7. Two independent filters guard the result: retention time plus a characteristic transition · Matrix peaks almost never pass both the time filter and the transition filter together.
  8. It watches only chosen precursor to fragment transitions, so noise is rejected · Watching chosen transitions drops everything that fails either filter.
Worksheet · LightMySky