What mass spectrometry is used for
- Finding relative isotopic mass.
- Finding the relative abundance of isotopes.
- Calculating relative atomic mass.
- Determining relative molecular mass (Mr).
- Helping identify simple organic compounds from fragmentation patterns.
Key knowledge students should learn
- How to read simple mass spectra of elements.
- How to use isotope abundances to calculate relative atomic mass.
- How to identify the molecular ion peak.
- How to use the m/z value to interpret spectra.
- How fragmentation produces smaller peaks that give clues about structure.
Time-of-flight mass spectrometry
For some exam boards, especially AQA, students are expected to know the basic stages of a time-of-flight (TOF) mass spectrometer:
- Ionisation
- Acceleration
- Ion drift
- Detection
- Data analysis
Board differences at a glance
AQA
Emphasises TOF principles, isotopes, simple spectra of elements, and using mass spectrometry to determine relative molecular mass.
Edexcel
Includes isotopes and Mr, plus molecular ion peaks, fragmentation, and accurate mass in analytical topics.
OCR
Places mass spectrometry within analytical techniques, including isotope calculations, fragmentation analysis, and structure deduction.
Typical exam-style tasks
- Calculate Ar from isotopic abundance data.
- Identify the molecular ion peak.
- Determine the Mr of a compound.
- Explain why peaks appear at different m/z values.
- Use fragmentation peaks to suggest a simple structure.