Analyser of Quadrupole and time of flight.Mass Analysers.
Summary of Mass Analyser.
Quadrupole mass spectrometer.
Factors Affecting Function Of Quadrupole.
Principal, Construction & Working.
Linear Time of flight mass spectrometer.
Time Of Flight Mass Spectrometry, Need For Variant Type Of Time of Flight Analyser.
Variant Of Linear TOF Analyser.
Ion mirror / ion reflectron / reflectron. Time-lag focussing.
Advantages, Disadvantage, Application.
1. Analyser of Quadrupole and
time of flight
Presented By -
Nishinandan R. Suryawanshi
Roll No - 5006
Guided By –
Dr. Vivek B. Panchabhai
Channabasweshwar college of pharmacy,
Latur
2. Contents :
Introduction
Principle
Theory
Construction & Working
Variants
Advantages
Disadvantages
Applications
3. Introduction
Mass spectroscopy is an analytical chemistry
technique that helps to identifying the
amount & type of chemicals present in a
sample by measuring the mass-to-charge
ratio and abundance of gas phase ions.
Define:
A type of mass spectrometry where
the mass-to-charge ratio of the sample ions
is measured whilst the ions are held in a
stable orbit by an electric field generated by
four parallel electrodes.
4.
5. Mass Analysers
Mass analyzers are called heart of mass
spectrometer.
These are the instrument which separate
the mixture of ions that are generated
during the ionization step by m/z in order
to obtain a spectrum.
6. Types of mass analysers
Magnet sector mass spectrometer
Quadrupole mass spectrometer
Ion trap mass spectrometer
Time of flight mass spectrometer
Fourier transform mass spectrometer
7. Summary of mass analysers
Mass Mass Range Resolutio
n
Sensiti
vity
Magnetic sectot 1-15000 m/z 0.0001 Low
Quadrupole 1-5000 m/z Unit High
Ion trap 1-5000 m/z Unit High
Time of flight Unlimited 0.0001 High
Fouriier
transform
Up to 70k
Da
0.0001 High
8. Quadrupole mass spectrometer
Quadrupole mass analysers concept was
first reported by Paul and Steinwedel in the
1950s.
Quadrupole consists of four rods which are
arranged parallelly.
Rods opposite to one another are
electrically connected.
Ions are separated based on m/z at a
particular DC and Radiofrequency voltage.
9. Principle
Ions from the ions sourcw
Quadrupole analyser with a constant DC
& RF voltage
At given combination of DC & RF
voltage
Ions with certain m/z values reach the
detector
Ions with different m/z values travel
unstable path
11. Construction
It consists of four electrically conducting
parallel rods.
One diagonally opposite pair of rods is
held at +Udc volts and the other pair at –
Udc volts.
A radiofrequency oscillator supplies
+Vcosωt to the first pair and –Vcosωt to
the second pair.
Ions enter to the quadrupole through a
circular aperture.
12.
13. Ex.
CO2 molecules have
quadrupole–quadrupole
interactions with each other.
The central carbon carries a
partial positive charge, while
the terminal oxygens carry
partial negative charges.
The like-charge atoms have
repulsive electrostatic
interactions (+/+ and -/-)
while the oppositely-charged
atoms have attractive
electrostatic interactions
(+/-).
15. ADVANTAGES:
High sensitivity.
They can operate close to ground potential.
Ideal for interfacing to LC system and for
atmospheric pressure ionization (API)
techniques such as electrospray.
Well suited for the negative ions ,since the
analyser does not discriminate between the
polarity of the ions.
Economic, robust and scanning is very fast
16. DISADVANTAGES:
Quadrupole is generally inferior to
magnetic sector analyser with respect to
resolution and mass range.
Peak height variable as a function of
mass.
Not well suited for pulsed ionization
methods.
17. APPLICATIONS
In liquid chromatography-Mass
spectrometry.
In Gas chromatography-Mass
spectrometry.
To measure the relative amounts of
different gases in a mixture.
Proteomics.
18. TIME OF FLIGHT MASS
SPECTROMETR
Introduction :-
Stephens first described the concept of
time of flight in 1946.
As the name implies, time of flight mass
spectrometer separates ions and measure
their m/z based on the time they take to
pass
( “fly” ) from the ion source to the
detector.
19. PRINCIPLE
Ions with different masses and same
kinetic energy travel when accelerated and
the ions with smaller masses (less m/z
value)reaches early to the detector than
the bigger masses .
20. THEORY
The kinetic energy of ions of mass (m), charge (z)
and accelerating potential (V) is given by
KE = zV = ½ mv2 (1)
Where (v) is velocity of the ions which is given by
v = l/t
where, l = length of the tube
t = time taken by the ions to pass the length of the
tube
Therefore, equation 1 becomes
zV = ½ ml2/t2
m/z = 2Vt2/l2
2V/l2 = k (constant)
therefore, m/z = kt2
m/z α t2
21.
22. Working
IONS FROM THE ION SOURCE
//
TOF
//
ACCELERATION OF IONS
//
ACQUIRES DIFFERENT VELOCITIES
//
SPATIAL SEPARATION OF IONS IONS
//
WITH HIGHER VELOCITY REACH THE
DETECTOR FIRST
23. NEED FOR VARIANT TYPE OF
TOF ANALYSER
Ions with very similar m/z ratio may have
relatively poor mass resolutions .
This is due to the spatial distribution in
the ion source and their proximity to the
applied electric field, not all the ions
receive the same kinetic energy.
This leads to components in mixtures
being unresolved from one another and
large errors in molecular weight
measurements.
24. VARIANTS OF LINEAR TOF
ANALYSER
1. Ion mirror / ion reflectron / reflectron.
For ex. Consider two ions of the
same m/z ratio that having slightly
different kinetic energy.
25. 2. Time-lag focussing
In time-lag focusing TOF applying
accelerating potential is delayed.
Ions from the ion source will have some
kinetic energy and moves with different
velocities
Application of potential gives more
energy to the ions which are away from
the detector than closer to it.
The amplitude is adjusted in such a way
that all the ions reach the detector at the
same time.
26. ADVANTAGES
Mass range is unlimited.
Excellent sensitivity due to lack of
resolving slits.
DISADVANTAGES
Limited use in case of pulsed ionization
techniques.
Mass resolution is usually less than 20000.
Fast electronics are necessary for adequate
resolution.
27. APPLICATION
Due to its fast scanning capability it is
increasingly being used in LC-MS
instrumentation.
Generally it is used in case of fast analysis
or in high chromatographic resolution
techniques.
28. REFERENCE
Spectrometric identification of organic
compounds by Robert M Silverstein and
Francis X Webster,pg. no. 10-12.
Instrumental methods of analysis ,7th
edition by Willard Merrit Dean Settle, pg.
no. 480-483.