L40 - Mass Spectrometry Flashcards
What is the definition for spectroscopy?
Hohw matter interacts with electromagnetic radiation - theory
What is the definition for spectrometry?
The application of spctroscopy to produce results - practical
What is the spectrometer?
The instrument used to measure
What is mass spec?
An analytical technique used to measure the mass of charged ions
What are the steps in mass spec?
- molecule ionised
- forms molecular ion “parent ion” // M+ or M-
- fragmentation occurs
- into a number of dif species “daugther ions”
What are the 2 components of the mass spectrometer?
- ionisation - molecules need to be charged
- separation of charged ions
What is the m/z?
- Ratio mass to charge
- But z = 1, consider it as mass of the ion
How can ionisation be achieved?
- electron ionisation/electron impact
- chemical ionisation
What is electron ionisation/electron impact like?
- hard technique
- generates radical cation M+ in +ve mode (e- removed), anion M- in -ve mode (e- added)
- results in lots of fragmentation
- mass of M+/M- nearly same as M
What is chemical ionisation like?
- soft technique
- generates ions through protonation = MH+, deprotonati8on = M-H-
- less fragmentation
What is the separation of charged ions?
- ionisation of compound = charged species
- stars to fragment
- ions deflected by magnetic field
- different sizes travel dif distances
What can mass spec be used to do?
Identify a compound in different ways
- HRMS/parent ion peak
- through different ionisation peaks
What can you use HRMS for?
Predict molecular formular of compounds (due to different exact masses), not arrangement
What is fragmentation like in different molecules?
Different molecules with the same parent ion have different fragmentations
What do you use exact mass for?
For mass spec/analysis of single molecules
What do you use molecular weight for?
Yield calculations - calculated using the average of isotopes
What does the nitrogen rule apply to?
Neutral molecules (M+/M-)
What is the nitrogen rule?
- compounds containing C, H, N, O, S and the halogens are EVEN MW
- compounds containing an odd number of N atoms are ODD
