Into To Mass Spec Flashcards
Mass spectrometers are able to
- measure atomic and MW of charged species
- analyse low sample levels
- analyse compounds in mixtures
Definition of mass spec
The process of weighing molecules based on the ratio between mass and charge
Mass spectrometers are unable to
- detect neutral molecules and radicals
Definition if isotope
Atoms of the same element with different numbers of neutrons in atomic nucleus
Add mass but not charge
Mass accuracy definition
Half (distance between MW/MW of highest) in ppm
Definition of mass resolution
The ability to separate two ion signals from one another in a mass spectrum
Basic components of a mass spec
Ion source
Mass analyzer
Ion detector
Examples of ion sources
- MALDI
- electrospray ionization
Explain MALDI
Matrix assisted laser desorption ionization
- analyte of interest mixed with matrix compound that efficiently absorbs laser wave length
- allows ionization of sample molecules through electron transfer
Types of mass analysers
TOF
Quadrupoles
Quadrupole ion trap
Ion cyclotron resonance
How does a reflector TOF MS work?
The reflect extends the light tube to almost twice the length
Ions with greater kinetic energy pass further into the reflection before being repelled
How does a quadrupole ion trap work?
Ions are trapped in a small interior volume between conical lenses
Raising or lowering the voltages on the entrance and exit trap electrodes controls the movement of ions
How does the ion cyclotron resonance work?
Traps make use if magnetic field
Describe tandem MS/MS
Have multiple mass analysers
Allows selection and isolation of specific ions
Two mass analysers separated by a collision cell
Collision induces dissociation of parent molecule into a series of daughter fragments
