Introduction
In this article we discuss about mass spectroscopy which include what is mass spectroscopy?, mass spectroscopy principle, instrmentation, working and its application with advantages and disadvantages.
What is Mass Spectroscopy ?
Mass Spectroscopy is a analytical technique which is used to seperate sample based on mass into charge ratio. in vary short we understand let’s understand how its work. so sample which we are working are injected into instrument so sample pass through electric and magnetic feild and finally detector detect the sample and show into computer screen in the form of graph. Graph which we visualised in computer screen have different different picks which is due to molecular weight of different different molecule.
By interpretation of graph on computer screen we can get information about what is different different weight of moleculein sampleso that’s is a reason we called its mass spectroscopy.
What is Principle of Mass Spectroscopy?
The principle of mass spectrometry depend upon ionization of the sample and if sample get ionize so it’s separation of ions based on their mass-to-charge ratio, and detection of the separated ions to determine the chemical composition of the sample with the help of detector.
Uses Of Mass Spectroscopy
- We can use mass spectroscopy to isolate isotopes, because isotopes have different-diffrent mass such as C12, C14, C13,etc.
- To Detect molecular fragments: If some compound is fragmented by using some technique, we can know the mass of each fragment using mass spectrometry technique or we can say that to study paticulat atom or molecule in sample we can use mass spectrometry technique.
Instrumentation Of Mass Spectrometry
- Sample Inlet
- Ionization Chamber
- Acceleration Plate
- Velocity Selector
- Two Big Magnet
- Detector
- Computer Screen
Sample
In mass spectroscopy we can used as sample as any form solid, liquid and Gas as well but due to different sample phase here ionization is difficult by using one ionization method, so we used different – different ionization method to ionized different phases sample such as solid, liquid and gas, on basis of ionization method we devided mass spectroscopy into different different types.
Ionization Process
Electron gun which is present in ionization chamber release high energy electron which are contact with sample molecule atom, in sample atom elctron cloud is present which have an electron on it, so highly energy electron which is release by electron gun eject electron present in sampleatom and make a atom positive chargeon it. so in ionizationstep positive charge are formed.
Acceleration Phase
Now positive charge is formed by ionization process, this positive charge is accelerate by accelerator which have negative charge plate. Due positive charge of atom negative charge plate attract positive charge atom and increases the speed of atom and now atom inter into next steps.
Velocity Selector
Question arises here why we need velocity selector? so reason behind is that when different – different velocity charges molecule hit the detector, detector can’t interpret them and not able to generate proper graph, so we have to select particular velocity so detector can detect easily. now let’s know how velocity selector work? In velocity selector two electric plates are present which generate electric field along with two big magnets which are present perpendicular to electric field. so the relation between electric and magnetic field is
Fm =F e
q.V.B = Q.E
Q = Charge
V = Velocity
B = Magnetic Field
E = Electric Field
m = Mass
So, the relation between mass and velocity is directly proportion as follow, F.m = QVB , Here Force, mass, charge and magnetic field are constant, so as you see mass is directly proportional to the velocity of atom.
- If velocity of molecule is greater so magnetic force on that molecule is greater and if less magnetic force velocity is laso less.
- So due to greater magnetic field atom attracts towads magnet. and bote B and E force are equal so if less magnetic fielf exert on molecule there is more electric force and atom move towards electric field or electric plates.
- In Conclution atom which has higher speed it move towards magnet, and atom which has lower speed it move towards electric field. in this way specific velocity molecule only cross the area of velocity selector and rest are not.
Two Big Magnet
- Now the specific velocity of molecule inter into the magnetic field which produced by two gient magnet present next, these magnet apply equal amount of magnetic field to all charge molecule, and result of applying magnetic field charge molecule formed curve shaped trajectory and fall to detector.
- different molecule formed different radius of curve , small molecule molecule formedshort curve while large molecule formed large curve and radius is more.
- Detector detect the radius which atom fall on that and give graph on computer screen.
F.m = Fc
Q.V.B = MV2/R
Q.B = M.V/R
R = M.V/Q.B
So, in above formula radius is directly proportional to mass if radius is more mass is greater and we can know the mass of molecule by this technique.
Limitation
- Mass spectroscopy is highly sensitive it may not always detect the low abundance atoms present in sample.
- Sometime lack of resolution it can not distinguish between closely related atom present in sample. Mass spectroscopy is also expensive and it not available in all laboratories.
- Mass Spectroscopy sample preapration is also tough and it’s required lot’s of time to preparesample.
