Mass Spectrometry

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  • Created by: LBCW0502
  • Created on: 27-01-18 16:27
What is mass spectrometry?
A technique used for measuring the molecular weight and determining the molecular formula of an organic molecule
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Describe the process of using a mass spectrometer
Sample is vaporised. Bombarded with electrons. Cations decompose to form fragments. Acceleration towards negatively charged plate. Passed through curved analyser tube in a magnetic field which are deflected depending on m/z ratio
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What are the labels on the axes for the mass spectrum?
Intensity against m/z ratio
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What is M+?
The molecular ion
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Does a mass spectrometer measure the masses of all individual molecules?
Yes
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What is the base peak?
The tallest peak in the mass spectrum (100% relative abundance)
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What is fragmentation?
The decomposition of the molecular ion into lower molecular weight fragments
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What is the M + 1 peak?
Usually indicates an isotope
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What is the nitrogen rule?
A compound that contains an odd number of N atoms gives an odd molecular ion (vice versa)
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What is the M + 2 peak?
Indicates two peaks in a ratio for molecular ion (e.g. alkyl halides, 3:1 for Cl/Cl atom present, 1:1 for Br/Br present)
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Values in high resolution mass spectrometry are measured to how many decimal places?
4
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Describe GC-MS
GC separates mixture and MS analyses mixtures in compound. Sample injected into GC, vaporised, carried using gas, separation based on b.p or affinity for stationary phase. Passed through MS. Plot amount vs retention time
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What is ESI?
Electrospray ionisation. Forms ions by creating a fine spray of charged droplets in an electric field. Evaporation of the charged droplets forms gaseous ions that are then analyzed by their m/z ratio (analysis non-volatile compounds)
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What is wavelength?
Distance from one point on a wave to the same point on the next wave
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What is frequency?
The number of waves passing a point per unit time (cycles per second)
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What is the equation for the speed of light?
Speed = wavelength x frequency
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What is the equation for energy?
E = hv
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What is Planck's constant?
6.63 x 10^-34 J.s
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What are the sections of the EM spectrum?
Radio, microwaves, infrared, visible, UV, X-ray, gamma
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Are nuclear spin states quantised?
Yes
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What must happen for absorption to occur?
The energy of the photon must be equal to the difference between the two energy states (delta E)
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How does the energy between the two states correspond to the energy of radiation needed for absorption
The larger the energy difference between two states, the higher the energy of radiation needed for absorption, the higher the frequency, and the shorter the wavelength
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Other cards in this set

Card 2

Front

Describe the process of using a mass spectrometer

Back

Sample is vaporised. Bombarded with electrons. Cations decompose to form fragments. Acceleration towards negatively charged plate. Passed through curved analyser tube in a magnetic field which are deflected depending on m/z ratio

Card 3

Front

What are the labels on the axes for the mass spectrum?

Back

Preview of the front of card 3

Card 4

Front

What is M+?

Back

Preview of the front of card 4

Card 5

Front

Does a mass spectrometer measure the masses of all individual molecules?

Back

Preview of the front of card 5
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