Flashcards
Untitled
Cards in this deck (22)
- 1Mass spectrometerAn instrument used to measure the Relative Mass of Isotopes
- 2Time of flight masssspectrometry occurs under a vacuumNo other particles interfere with the experiment
- 3IONISATION (Electrospray Ionisation)- sample dissolves in a volatile polar solvent
- injected through a needle at a high voltage
- each particle becomes ionised by gaining a proton (H+)
X(g)+ H+————>XH+(g) - 4ELECTRON IMPACTHigh energy electrons from an electron gun
- fired toward a sample and knock off an electron
X(g)—-> X+(G) + e- - 52. ECCELERATION- +ions accelerated by the electric field to a constant KE
(Velocity- depends on mass of ion)
———-_
Iona with lower mass- travel faster (higher velocity)
Higher mass- travel lower (lower velocity) - 6KE equationKE=1/2mv2
(All Pericles have same KE but different velocity ) - 73.ION DRIFTIona separate at this stage
- all Iona have a constant KE
- Iona are allowed to drift in a flight tube of a KNOWN DISTANCE and the Time that it takes for Iona to reach the detector is measured - 8What does TOF depend onVelocity which depends on mass of the ion
ION with lower mass- shorter time to reach detector - 9Mass of ion can be determined fromTime take. For ion to reach the detector
T=d/v - 10Stage 4: ION DETECTION+ Ion hit detector (- charged plate)and picks up an electron (current is generated when ion gains an electron)
- 11The greater the abundance of Iona hitting the plateThe bigger the current produced
- 125: DATA ANALYSISDetectors linked to amplifier which is linked to recorder (converts current into a peak and is shown on mass spectrum)
HEIGHT OF PEAK- PROPORTIONAL to size of the current generated and therefore proportional to the abundance of that ion - 13The peaks are displayed onPlot of abundance v mass/charge ration (m/z)
1+ usually produced mass/charge is the same as mass - 14Mass spectra of molecules…
- 15FragmentationCovalently bonded molecules bonds getting broken and breaking into fragments during electron impact ionisation by the electron gun
- 16Fragmentation will occur to sone but not all molecules . (DOME REMAIN INTACT AND JUST GAIN A + CHARGE)Unfragmented and + charged molecules will give us the greatest m/z value (molecular ion peak)
This peak tells us: the Mr of the molecule - 17ELECTRON IMPACT IONISATION- Mr of sample = to peak with greatest m/z value (furthest right)….
- 18Electrospray ionisationVery little fragmentation occurs (much less peaks in the mass spectrum)
- 19To find the mr of somethingYou must minues 1 (mass of proton added during ionisation)
- 20With Electrospray ionisation The Mr of the sample will be…Equal to the peak with the greatest m/z value take away 1
- 21Chlorine atom1 - (3:1)
2 - (9:6:1) - 22Bromine1-(1:1)
2- (1:2:1)
Information
- Description
- Flashcards on Untitled, created by Ellaine Wahome on 10/10/2022.
- Created by
- Ellaine Wahome
- Views
- 0
- Rating