Mass Spec Flashcards
what is Mass Spec?
Analytical method to measure molecular or atomic weight
components
1) Ion source : charge atom/ molecule = Gas
2) Mass analyzer : separates ions with diff m/z
3) Detector : see ions
Units
Daltons
1 Da=1g/ mol
% mass accuracy
measured - True / True x 100
PPM accuracy
Measured - True /True x 10 ^ 6
Sensitivity expression units
Molar fraction ( pmol) or grams (mg) per volume fraction
Lower= Better
Signal to noise ratio
compares levels of desired signal to background noise
LOD + LOQ
Limit of Detection + Limit of Quantification
Resolving Power
mass/ (Delta) Mass (peak width necessary for Separation
ESI principles
Molecules to Gas using high voltage power supply to charge liquid
Jet expelled + droplets repel = mist
Droplets evapourate leaving analyte
LC-MS
physical Separation Of HPLC with mass analysis
ESI benefits
very sensitive , Positive+ negative mode
MALDI-TOF on?
High molecular mass + thermoliable , non- volatile compounds
MALDI - TOE Benefits
Easy to use, tolerant to buffers
Matrix of MALDI-TOF
must have conjugated Structure to absorb light
Protects analye + facilitates charge transfer
TOF analyzer
Uses Reflectron (Reflect ions back)
Longer tube = Better resolution
smaller m /z = quicker
Same charge= Bigger mass first vice versa
Quadrupole Mass Filter
stable ions pass through to detector
unstable removed
Tandem Mass Spec
Multiple analyzers generate structural info
E -g 1= Select ion, 2= fragments ion, 3= Analysis of fragments
collision induced Dissociation
ion collides with collision gas = fragmentation
Product ion scan
lon focussed, collisions, scanning of products
precursor ion scan
Scans precursor on
BMS applications X3
structures of biomolecules, How drugs are used in body, Forensic analysis
protein ID Top down
Direct protein sequencing= whole protein
Protein ID Bottom up
Protein cut by Trypsin at certain amino acids = Peptide
Peptide Bond
Carboxyl group reacts with amino group= Release water
b ions (left)
mass of amino and +1 ( Sum of N-term )
y ions (right)
mass of amino acids +19 (sum of OH group )
Multidimensional L C-MS
HPLC+ MS (fractionate + analyze all )
Mass fingerprint method
2D electrophoresis, cut out, Trypsin digestion, extract, Mass spec, Data search
