3.3.6.2 Mass spectrometry Flashcards
What is mass spectrometry?
It is used for measuring the atomic masses of atoms and the relative molecular mass of organic compounds
What is a mass spectrum?
A graph of relative abundance against the mass/charge ratio
Usually to the nearest whole number
Some measure to 3 or 4 decimal places
What is the charge of carbon compounds?
Most have a +1 charge so the horizontal axis on a mass spectrum is relative mass
What is gas chromatography mass spectrometry?
When a stream of gas is used to carry a mixture of vapours through a tube packed with a powdered solid
Different components emerge from the tube at different times
This creates a mass spectrum
How do you work out the molecular formula from a mass spectra?
Add up the accurate atomic masses plus
What are the main parts of a mass spectra?
Peak with the highest m/z = molecular ion peak, mass of a +1 ion, m is the Mr of the substance
Parent peak = Mr of compound
Peak not representing the Mr = isotopes
Base beak = peak from the most abundant fragment, set at 100% intensity
What are the two types of mass spectra?
Y axis = relative abundance: peaks add up to 100
or
Y axis = relative intensity
What should you remember about mass spectra?
Fragments that give a peak are positive ions
Fragments that have been lost are radicals
