Mass Spectometry and Separation Techniques Flashcards
TOF
Time of Flight
Explain this concept used in Mass spectrometry.
Sample is vaporised and ionised in a vaccum.
This causes particles in the sample to accelerate.
Small ion move quicker and changes direction from path easily. This relates to Newton’s Law: mass is proportional to acceleration.
A charged detector checks the time in the flight path and from this we can get the mass.
What is a Hexapole?
How does it work?
Remember there is also an octapole, quadrupole etc.
a hexapole is like a traffic controller for charged particles, making sure they stay on course before they reach the mass spectrometer’s detector!
Has 6 poles.
A hexapole is a device used in MS (including TOF-MS) to manipulate ions. It is also used in In tandemMS.
Since heavy ions cannot change directions quickly to respond to a change in voltage, it can therefore separate ions based on how quickly they react to a change in voltage.
What is Tandem Mass Spectrometry?
Tandem MS
MS-MS
Regular MS tells you the weight of a box.
Tandem MS opens the box and tells you what’s inside!
Uses two types of MS
E.g. Hexapole followed by TOF.
Tandem MS is like a two-stage detective process in mass spectrometry. Instead of just measuring the mass of molecules, it breaks them apart and analyzes the fragments to get even more information.
Separation techniques for Mass Spectrometry.
1) Gel Permeation Chromatography
GPC
Explain how this works.
What is its other name?
What is one disadvantage of this method?
Also called Size Exclusion Chromatography.
Separates molecules based on size and how quickly they pass through the gel e.g. silica gel
Big kids (large molecules) can’t fit in the tunnels and just run straight through and come out first
Small kids (small molecules) explore every tunnel, taking much longer to get out.
Con: You do not get info on chemical properties such as acidity or functional groups.
Separation techniques for Mass Spectrometry.
2) Affinity Chromatography
This refers to regular chromatography
Separates based on properties like polarity, pH.
The plate is the stationary phase and the solvent is the mobile phase.
If the molecules are strongly attracted to stationary phase they move more slowly. So the highest affinity molecules is further down while the one with the least affinty is higher up.
GC, LC and HPLC use reverse phase chromatography.
Affinity chromatography uses normal phase chromatography.
Yes, where the stationary phase is nonpolar (hydrophobic) so non polar substances can be separated.
Yes, where the stationary phase is polar.
Separation techniques for Mass Spectrometry.
3) Ion chromatography
What are the two types?
Ion exchange and regular ion chromatography.
Regular ion: measures how long ions in a sample mixture takes to pass over a column.
Time is constant and characteristics e.g. Cl ions take 6 mins.
Ion exchange chromatography
Explain this technique.
Application: To purify hard water.
ions from a sample are exchanged for other ions.
The stationary phase is resin with cations/anions.
Ions with a stronger charge or higher affinity for the resin stay in the column longer.
Cation Exchange or Anion Exchange is reversible so the resin can be regenerated.
Separation techniques for Mass Spectrometry.
4) Gel Electrophoresis
Application: analysing blood samples at crime scenes.
separate molecules, like DNA, RNA, or proteins, based on their size and charge.
prepare a gel with tiny pores.
sample is loaded into wells at one end of the gel, and an electric field is applied, causing charged molecules to move toward the opposite charge.
Smaller molecules move faster through the gel, while larger ones move more slowly, causing them to separate by size. After the run, the gel is stained and visualized under UV light or other detection methods to see distinct bands representing the separated molecules.
PAGE (Polyacrylamide Gel Electrophoresis) is a specific type of gel electrophoresis used mainly for separating proteins or small nucleic acids based on their size.
Just note
