Mass Spectrometry Flashcards
What can mass spectrometry be used to determine?
the accurate molecular mass and structural features of an organic compound.
It terms of the quantity of the sample, how much does mass spectrometry require?
a very small amount
Decribe in detail fragmentation.
The sample is vaporised and bombarded with electrons. This results in the formation of positive ions due to the loss of one (or more) electrons.
Either the whole molecule (parent ion) or part of the molecule (ion fragments) are ionised.
Usually only ions with a 1+ charge are produced.
Describe in detail deflection.
The positively charged parent ions and ion fragments from the source are then accelerated through a powerful magnetic field, causing the ions to adopt curved trajectories.
The path of the ion will depend on its mass and charge.
Heavier ions will be deflected less than lighter ones.
Describe in detail detection.
As the magnetic field strength varies, ions with different mass/charge ration (m/z) are focused onto a detector. This gives a mass spectrum, which consists of a series of peaks showing the relative abundance of ions with different m/z ratios.
What is the most abundant peak called?
base peak
What is the base peak assigned?
an abundance of 100%
What are other abundances given?
smaller percentages, relative to the base peak
What can molecular ions either be in terms of stability?
stable enough to remain intact during their progress through the mass spectrometer, or will have sufficient energy imparted by the collision of electrons to break specific bonds, thus producing a pattern of fragment ions at the detector.
What is the relative abundance of a fragment related to?
its stability.
