Lecture 5: Fundamentals of Mass Spectrometry: Hardware Flashcards
what are the components of the mass spectrometer?
inlet, source, analyser, ion detector, data system
what does the ion source produce?
ions of the analytes
what does the analyser do?
analyzer manipulates the ions according to their mass-to-charge (m/z) ratio.
what does the detector system do?
The detector system detects the ions and records the relative abundance of the ion species.
If the ion source for gas sample what can it be?
Electron Ionization (EI) Chemical Ionization (CI)
what the common liquid ion source?
Electrospray Ionization (ESI)
what happen with gas sample ionisation?
Not just an ion being formed there will be a charge.
what are two types of ionisation?
hard and soft
what are hard ionisation techniques ?
Electron Ionisation (EI)
what produces more fragments hard ionisation techniques soft?
hard produces more
soft ionisation techniques are what?
Chemical ionisation (CI), Fast Atom Bombardment (FAB), Electrospray ionisation (ESI)
what better for determining molecular mass, soft or hard?
soft ionisation techniques
How does electro ionisation work?
- Molecules are ionized during collision with a beam of high energetic electrons
- Electrons are “boiled off” in a filament
what energy is the beam in electron ionisation?
(typical 70 eV energy)
EI is great for finding the?
identification of structures
what does the high internal energy during EI equal?
Due to high internal energy high degree of fragmentation (which occurs IN ion source)
with EI what do u get?
mass spectrum
CI: what are the 3 common reagents gases?
Methane (CH4), iso-butane or ammonia (NH3)
CI: Electron bombardment of reagent gas produces what?
reagent ions
CI: Each gas has a ______ proton-affinity (PA) with the molecule
different
In mass spec _____ things happen.
unusual
how is a reagent ion made?
the gas has a proton added
what is chemical ionisation useful for?
Useful in determination of the molecular ion (don’t know what fragments we have)
what ions can be tested?
you can only analyse either positive or negative ions, not both together , positive more common
CI: what if a compound does not accept a proton?
hydrogen would donate on because it owns accept,
what happen sin ammonia is a reagent gas in CI?
- form radical cation
-forms with another ammonia molecule (NH4+)
-donates proton to molecule, returns back to ammonia - or may donate the entire nh4+ to the molecule
(depend son affinity of compound) - can lead to two
in chemical ionisation what will change?
molecular mass, because proton or NH4+ is added to your compound
if methane gas in CI?
add proton , mass increase by 1
compounds with a low proton affinity have a proton?
taken away
in CI negative ions may form but we do not?
measure them , focus on positive ions
In EI the repeller should be ?
positive to look at positive ions
when is API used?
when we have. liquid sample
what are the two types of Atmospheric pressure Ionization ?
ESI
APCI
ESI is a ___ technique.
soft
(API)’s are useful for what?
useful for the analysis of large non-volatile chargeable molecules such as proteins and nucleic acid polymers.
what gas is around the capillary in ESI?
high stream of gas, nebuliser , creating spray or mist.
why does ESI require a spray?
smaller droplets, easy to evaporate solvents
How do we get rid of solvent molecules in ESI?
there is a heated area allowing the solvent to evaporate, the sis easier with fine droplets form the spray
in ESI the entire ESI is put through what volt?
high voltage around 400.
what does the high voltage in ESI do?
charge the solvent, proton gets added to analyse, ending in a charge analyte.
How do we separate ions?
using a mass analyser
what are the types of mass analysers?
Quadrupole (Q)
Ion Trap (IT)
Time-of-Flight (TOF)
Magnetic sector instruments
what mass analyser are we focusing on?
Quadrupole (Q)
what happens in the quadruple?
it has 4 separate rods with a space in the middle
