Chapter 21 - Mass Spec Flashcards
Mass Spec
Technique used studying the masses of:
1.
2.
3.
- atoms
- molecules
3, fragments of molecules
How does Mass Spec works:
- ______ ______ are ionized
- Ions are ______ by an _____ ______ and separated by their ____ __ _____ ratio with a magnetic field
- _____ detects them
- Gaseous species
- accelerated, electric field, mass-to-charge
- detector
Magnetic field:
1. ions that are too small bend ______
- ions that are too heavy bend _____
- ions that have the right mass ______
- too much
- too little
- can enter the detector
Ionization Sources:
- What are the two types of ionization?
- Electrons emitted form a ___ _____ are accelerated ( __ V)
- a molecule needs about ___ to ____ V to be ionized
- What is this symbol, M+•? what does it break into?
- Electron and Chemical
- hot filament, 70
- 12 to 15 V
- molecular ion that breaks into fragments.
- a peak that is one mass unit higher than the M+•, small peak
- typically the peak with the high m/z value, first ion produced by electron ejection in electron ionization mass spectrometry
- the most intense, (largest), peak in mass spectrometry
- M+1 peak
- molecular ion, M+• peak
- base peak
Ionization Sources - Chemical:
Produces ____ fragmentation than ____ _____
- ionization sources is filled with _____ gas like ____
- Energetic electrons (____) convert ____ into a variety of reactive products
___ is a potent proton donor that reacts with the analyte to give ___ which is usually the most ________ ion in the chemical ionization mass spectrum.
less, electron ionization
- reagent, methane
- (100- 200 V), CH4 (methane)
CH5+, MH+, abundant
Mass Analyzer - Magnet:
- Ions with different mass, but constant kinetic energy, are separated by their trajectories in a magnetic field.
- Double-focusing MS: Ions ejected from the source pass through an electric sector as well as a magnetic sector.
- what does it help the peaks with?
- Magnetic Sector
- Double-focusing MS
- Helps resolution with peaks
Mass Analyzer - Quadruople:
Consists of _____ parallel metal rods to which are applied both with:
_____ voltage
________ _______ voltage
The electric field _____ ions in complex trajectories as they travel, allowing only ion with ____ particular m/z ratio to reach the detector.
Other ions collide with the rods and are lost before they reach the detector.
four
constant, radio-frequency oscillating
deflects, one
Mass Anlayzer - Time of Flight:
Ideally all ions have the _____ kinetic energy (½mv2) so ____ masses will travel at different speeds.
Lighter ones travel faster.
Long, straight, evacuated tube with the source at one end and the detector at another.
Bent for space saver reasons.
Ions expelled from the source, _____ to the detector in order of _____ mass.
same, differnet
drift, increasing
Mass Analyzer - Ion Trap:
Use a combination of ___ or ___ fields to “trap” ions inside the mass analyzer.
3D trap
Liner trap
Orbitrap
electric, magnetic
The MS can be highly selective for the analyte of interest. Issues: \_\_\_\_ amount of sample P\_\_\_\_ T\_\_\_
Giant
pressure
temperature
Liquid from the chromatography separation enters the nebulizer capillary with a stream of N2 gas and with a strong electric field, an aerosol of charged particles is created.
Little fragmentation of the analyte occurs.
electrospray ionization
Uses more than one MS
Tandem MS
First step: Some form of fragmentation creates a ____ ______
Second step: Precursor ion is ____ and _____ ions are formed.
Third step: Product ions are _____ and _____ by another MS.
creates a precursor ion
fragmented, product
separated, detected
what type of tandem MS
A mixture of ions enters Q1, which passes just one selected precursor ion to the second stage, Q2.
Q2 passes all ions of all masses straight on to the third stage, Q3.
Q2 is the collision cell which the precursor ion collides with an inert gas and breaks into fragments called product ions.
Q3 allow only specific product ions to reach the detector
triple quad
