Unit 9 pt2 Flashcards
Mass Spectroscopy
Design of a mass spec?
1) Entry chamber- gasses let in
2) Electron Gun- high energy electrons to ionise
3) Accelerator- Negatively charged metal plates make the ions go fast
4) Analyser- another electric field is passed over sample giving all same kinetic energy and passes them to a magnetic field
5) magnetic field- Circular path, separated by mass and charge
6) detector- draws line when ions arrive, higher line when there’s more
What does the electron gun do?
Sends high energy electrons at the sample to ionise it. The force can make molecules fragment
What does the accelerator do?
It is a series of negatively charged plates which speed the ions up
What does the analyser do?
it passes another electromagnetic field over the ions which makes them move in a curved path with the same kinetic energy
What does the magnetic field do?
it subjects ions to magnetic field making them move in circular path, they are now separated due to mass and charge
What does the detector do?
the detector picks up when ions arrive and draws a line, the higher the line the more ions have arrived at that time
What is used as the standard for comparison?
Carbon 12. It is said to be exactly 12 units
Why do you use whole numbers for masses in mass spec?
Because of mass defects
When you get the results what will be on the bottom of the graph?
mass to charge ratio (m/e)
How can you calculate RMM (average mass)from mass spec of isotopes?
you see the m/e of each isotope times them by their abundance divide by 100 and then add together.
(m/e X ab%) + (m/e2 X ab%2) /100
What is the parent ion peak and where will it be?
it is the whole molecule just without an electron. it will be at the 2nd highest m/e because a fragment cant be heavier than the whole molecule
What is the M+1 peak?
it is +1 m/e of the parent ion peak. it indicates an isotope
