The document discusses the principles of chromatography. It describes how chromatography separates components in a mixture based on differences in their interactions with mobile and stationary phases. It discusses how Michael Tswett first demonstrated chromatography in 1903 and the key aspects of how it works. These include how retention time, partition coefficients, selectivity factors and efficiency parameters like plate number and height equivalent to a theoretical plate are used to characterize chromatographic separations.
ION EXCHANGE CHROMATOGRAPHY
ByM.Vharshini
B.Sc. Bio Medical Science
Sri Ramachandra University
ION EXCHANGE CHROMATOGRAPHY
Ion-exchange chromatography is a process that allows the separation of ions and polar molecules based on their affinity to the ion exchanger.
It can be used for almost any kind of charged molecule including large proteins, small nucleotides and amino acids.
Cations or Anions can be separated using this method.
PRINCIPLE
It is based on the reversible electrostatic interaction of ions with the separation matrix (i.e.)
The separation occurs by reversible exchange of ions between the ions present in the solution and those present in the ion exchange resin.
CLASSIFICATION OF RESINS
According to the chemical nature they classified as-
1. Strong cation exchange resin
2. Weak cation exchange resin
3. Strong anion exchange resin
4. Weak anion exchange resin
According to the Source they can -
Natural resins : Cation - Zeolytes, Clay
Anion - Dolomite
Synthetic resins: Inorganic & Organic resins
◘Organic resins are polymeric resin matrix.
The resin composed of –
Polystyrene (sites for exchangeable functional groups)
Divinyl benzene(Cross linking agent)-offers stability.
Ion exchange resin should have following requirements
»It must be chemically stable.
»It should be insoluble in common solvents.
» It should have a sufficient degree of cross linking.
»The swollen resin must be denser than water.
»It must contain sufficient no. of ion exchange groups.
Physical properties of ion exchange resins
Cross linking:
It affects swelling & strength & solubility
Swelling:
When resin swells, polymer chain spreads apart
Polar solvents → swelling
Non-polar solvents → contraction
Swelling also affected electrolyte concentration.
Particle size and porosity
Increase in surface area & decrease in particle size will increase the rate of ion exchange.
Regeneration
Cation exchange resin are regenerated by treatment with acid, then washing with water.
Anion exchange resin are regenerated by treatment with NaOH, then washing with water until neutral.
EXPERIMENTAL SETUP OF ION EXCHANGE CHROMATOGRAPHY
Metrohm 850 Ion chromatography system
Instrumentation of ion exchange chromatography
PRACTICAL REQUIREMENTS
1.Column
» glass, stainless steel or polymers
2.Packing the column
» Wet packing method:
A slurry is prepared of the eluent with the stationary phase powder and then carefully poured into the column. Care must be taken to avoid air bubbles.
3.Application of the sample
After packing, sample is added to the top of the stationary phase, use syringe or pipette.
This layer is usually topped with a small layer of sand or with cotton or glass wool to protect the shape of the organic layer from the velocity of newly added eluent.
4.Mobile phase
Acids, alkalis, buffers…
6.Stationary phase
The ionic
ION EXCHANGE CHROMATOGRAPHY
ByM.Vharshini
B.Sc. Bio Medical Science
Sri Ramachandra University
ION EXCHANGE CHROMATOGRAPHY
Ion-exchange chromatography is a process that allows the separation of ions and polar molecules based on their affinity to the ion exchanger.
It can be used for almost any kind of charged molecule including large proteins, small nucleotides and amino acids.
Cations or Anions can be separated using this method.
PRINCIPLE
It is based on the reversible electrostatic interaction of ions with the separation matrix (i.e.)
The separation occurs by reversible exchange of ions between the ions present in the solution and those present in the ion exchange resin.
CLASSIFICATION OF RESINS
According to the chemical nature they classified as-
1. Strong cation exchange resin
2. Weak cation exchange resin
3. Strong anion exchange resin
4. Weak anion exchange resin
According to the Source they can -
Natural resins : Cation - Zeolytes, Clay
Anion - Dolomite
Synthetic resins: Inorganic & Organic resins
◘Organic resins are polymeric resin matrix.
The resin composed of –
Polystyrene (sites for exchangeable functional groups)
Divinyl benzene(Cross linking agent)-offers stability.
Ion exchange resin should have following requirements
»It must be chemically stable.
»It should be insoluble in common solvents.
» It should have a sufficient degree of cross linking.
»The swollen resin must be denser than water.
»It must contain sufficient no. of ion exchange groups.
Physical properties of ion exchange resins
Cross linking:
It affects swelling & strength & solubility
Swelling:
When resin swells, polymer chain spreads apart
Polar solvents → swelling
Non-polar solvents → contraction
Swelling also affected electrolyte concentration.
Particle size and porosity
Increase in surface area & decrease in particle size will increase the rate of ion exchange.
Regeneration
Cation exchange resin are regenerated by treatment with acid, then washing with water.
Anion exchange resin are regenerated by treatment with NaOH, then washing with water until neutral.
EXPERIMENTAL SETUP OF ION EXCHANGE CHROMATOGRAPHY
Metrohm 850 Ion chromatography system
Instrumentation of ion exchange chromatography
PRACTICAL REQUIREMENTS
1.Column
» glass, stainless steel or polymers
2.Packing the column
» Wet packing method:
A slurry is prepared of the eluent with the stationary phase powder and then carefully poured into the column. Care must be taken to avoid air bubbles.
3.Application of the sample
After packing, sample is added to the top of the stationary phase, use syringe or pipette.
This layer is usually topped with a small layer of sand or with cotton or glass wool to protect the shape of the organic layer from the velocity of newly added eluent.
4.Mobile phase
Acids, alkalis, buffers…
6.Stationary phase
The ionic
HPTLC- Principle, Instrumentation and Software (Abhishek Gupta)Abhishek Gupta
HPTLC is the improved method of TLC which utilizes the conventional technique of TLC in more optimized way
It is also known as planar chromatography or Flat-bed chromatography.
This presentation contains all the topics related to column chromatography. That includes introduction, principle,apparatus, experimental aspects of column chromatography, application of column chromatography, advantage and disadvantage of column chromatography with reference.
fluid chromatography (SFC) can be used on an analytical
scale.
It is a combination of High performance liquid chromatography (HPLC)
and Gas chromatography (GC).
It can be used with non-volatile and thermally labile analytes.
It can be used with the universal flame ionization detector.
It is important to producing narrower peaks due to rapid diffusion.
It is important for the chiral separations and analysis of high-molecularweight
hydrocarbons.
Supercritical fluids are suitable as a substitute for organic solvents in a
range of industrial and laboratory processes.
HPTLC- Principle, Instrumentation and Software (Abhishek Gupta)Abhishek Gupta
HPTLC is the improved method of TLC which utilizes the conventional technique of TLC in more optimized way
It is also known as planar chromatography or Flat-bed chromatography.
This presentation contains all the topics related to column chromatography. That includes introduction, principle,apparatus, experimental aspects of column chromatography, application of column chromatography, advantage and disadvantage of column chromatography with reference.
fluid chromatography (SFC) can be used on an analytical
scale.
It is a combination of High performance liquid chromatography (HPLC)
and Gas chromatography (GC).
It can be used with non-volatile and thermally labile analytes.
It can be used with the universal flame ionization detector.
It is important to producing narrower peaks due to rapid diffusion.
It is important for the chiral separations and analysis of high-molecularweight
hydrocarbons.
Supercritical fluids are suitable as a substitute for organic solvents in a
range of industrial and laboratory processes.
Department of Chemistry /College of Sciences/ University of Baghdad
Subject: Analytical Chemistry 4
Second stage
2nd semester
Dr. Ashraf Saad Rsaheed
2017-2018
High performance liquid chromatography (HPLC) head points:
HPLC Advantages Vs GC
Instrumentation
HPLC System
Separations
Mobile Phase Reservoirs
Degasser
Aim of Gradient system
High/Low pressure gradient system
HPLC Pump Criteria
HPLC Pumps: Types
Reciprocating Pumps
Sample introduction
Manual Injector
Auto Injector
HPLC Modes
The Mobile Phase
Hydrophobic interaction
Common reverse phase solvents
Detectors
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Gas chromatography head points:
Invention of Chromatography
original chromatography Experiment
Common types of chromatography
Paper and Thin layer chromatography
How does chromatography work?
Theoretical Plate
gas chromatography
schematic of GC
carrier gas-supply
Injection port
sample Injection system
split/spitless Injection
sample valves
GC columns
open tubular columns
Temperature Control
Solid Support Materials
Particle size of Supports
The stationary Phase
Detection systems
Characteristics of the Ideal Detector
Flame Ionization Detectors
Thermal Conductivity Detector
Electron-capture Detectors
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Theory and Principle of FTIR head points:
What is Infrared Region?
Infrared Spectroscopy
What is FTIR?
Superiority of FTIR
FTIR optical system diagram
sampling techniques
The sample analysis process
advantage of FTIR
References
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Scanning Probe microscopy (AFM and STM) head point
AFM: Configuration of AFM
Parts of AFM system and Principle of AFM
Three Modes of AFM
AFM Instrument
Advantage and disadvantage
STM
Schematic Diagram
AFM and STM
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X-Ray Diffraction head points:
Introduction
History
How Diffraction Works
Demonstration
Analyzing Diffraction Patterns
Solving DNA
Applications
Summary and Conclusions
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Photovoltaics: Fundamental Concepts and novel systems
Energy levels -bands
Doping of semiconductors
Energy band alignments between different phases
Space charge layers
p-n junctions, Schottky barriers
p-n cells, Si cells, thin film cells
Schottky cells (solid and liquid junction)
p-i-n cells
Fundamental limits of photovoltaic cells
How to overcome/ bypass these limits
New generation cells (brief survey)
PV stability, efficiencies and economics
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What is Automobile??
Brief History of Automobile
Changes over the years...
Indian Automobile Industry
Main parts of an Automobile
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Nanoimprint Lithography head points:
Approaches: thermal and UV NIL
Properties of NIL
Overview. of NIL
Thermal NIL resists.
Residual layer after NIL.
NIL for large features (more difficult than small one).
Room temperature NIL, reverse NIL, inking.
NIL of bulk resist (polymer sheet, pellets).
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Presenting a topic based on introduction to nanoscience and nanotechnology.
what is nano?
certain nomenclature like nanotechnology, nanoscience, nanomaterial, nanoscale, nanometer and so on.
surface to volume ratio and quantum effect related concepts.
future applications.
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Top down and bottom up method, processing, flow chart of top down and bottom up approach, Application.
I hope this presentation helpful for you.
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Different types of Nanolithography technique.
Types: Electron beam lithography, Photolithography, electron-beam writing, ion- lithography, X-ray lithography, and related images, concepts and graphical views.
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Infrared Spectroscopy and UV-Visible spectroscopyPreeti Choudhary
Instrumentation of Infrared Spectroscopy and UV-Vis spectroscopy
Discuss the fundamentals and concepts behind Infrared and UV-Vis spectroscopy.
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Presenting a topic which is entitled: Detectors
Above topic includes:
Types of detector
phototube detector
photomultiplier tubes
silicon photodiodes
photovoltaic cells
advantages
multi-channel photon detectors
linear photodiode arrays
photodiode array
with basics of instrumentation and science technology
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Presenting a presentation on the topic of Column chromatography with including basics of chromatography, principles, equations, graphs and data related to it.
Topics which covered in this ppt is
Principle of chromatography
classification of chromatography
partition coefficient
chromatogram
Resolution
plate theory
determination of N
band zone broadening
rate theory
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Operational amplifier: inverting and non-inverting amplifier, Power bandwidth, slew rate: slew rate distortion, noise gain, band width product. cascade amplifiers- bandwidth, CMRR, PSRR, Open loop op amp characteristics.
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Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
3. Principles of Chromatography
Chromatography is the process of
separating components in a mixture from one
another based on difference in their
properties.
A common feature to all chromatographic
methods is the distribution of the components
between two phases, the stationary phase and
the mobile phase.
5. Principles of Chromatography
The first detailed description of chromatography is
credited to Michael Tswett, a Russian biochemist, who
separated chlorophyll from a mixture of plant pigments
in 1903.
He placed a small amount of mixture on a column
packed with powdered calcium carbonate (the
stationary phase) and washed the sample through with
petroleum ether ( the mobile phase).
6. Principles of Chromatography
As the sample progressed down the column the
various components moved at different rates. Sample
components are carried by the mobile phase through
a bed of stationary phase.
Each component produced a band that had distinctive
color . Thus the Greek word chromatography for
colour and to write. Although the colored bands were
part of this first experiment, color is not important for
the method to work.
8. Principles of Chromatography
Individual species are retarded by the
stationary phase based on various
interactions such as :
• Surface adsorption
• Relative solubility
• Charge
9. Partition/Distribution Coefficient
As the mobile phase bearing the solute enters the
column, the solute distributes itself between stationary
and mobile phase.
This distribution between the 2 phases is described by the
Distribution Coefficient ‘K’, defined as
K = Cs / CM
where Cs & CM refer to the concentrations of the solute
in the stationary and mobile phases.
10. Partition Coefficient
If the value of K = 1 then the solute is equally
distributed between stationary and mobile phases.
For K < 1, the solute travels faster through the
column because it spends more time in mobile
phase.
For K > 1, the solute will be retained in the
stationary phase or will exit the column after
longer time.
Different solutes will have different values of
distribution coefficients, so their movement
through the column will be of different rates.
11. Chromatogram
The detector produces a signal which is plotted
graphically on the chart of an electronic
recorder and is called a Chromatogram.
A chromatogram gives
• Qualitative information using retention time of
various peaks
• Quantitative data from peak area or peak height
of the components.
12. Chromatogram - Retention Times
tM = retention time of mobile phase (dead time)
tR = retention time of analyte (solute)
tS = time spent in stationary phase (adjusted retention time)
L = length of the column
13. Velocities : Linear rate of solute migration
M
R
t
L
t
L
v
=
=
µ
Velocity = distance/time length of column/ retention
times
Velocity of solute:
Velocity of mobile phase:
14. Retention time and volume
Retention time, tR - time required to reach the peak
maximum from the point of injection.
Dead time, tM - time required for the unretained species
to reach the peak maximum from the point of
injection.
Retention volume, VR – volume of mobile phase
required to elute a solute to a maximum from a
column.
.
16. Capacity and Selectivity Factors
• Capacity / Retention Factor (kA)– it describes
rate of migration of solute in a column or
relative indication of time spent by solute in a
column.
• Selectivity Factor (α) – It provides a measure
of how well a column separates the two
analytes
18. Capacity/Retention Factor
where kAis thecapacity factor for solute A.
• Its value should lie between 1 and 5.
• If k is less than unity, accurate determination
of its retention time is difficult.
• If its too large, elution time becomes
inordinately long
19. Selectivity Factor: can you separate from your neighbour?
MAR
MBR
M
MBR
B
M
MAR
A
A
B
A
B
tt
tt
t
tt
kand
t
tt
k
k
k
K
K
−
−
=
−
=
−
=
=
=
)(
)(
)()(
α
α
α
B retained more than A α >1
20. Selectivity factor
• The selectivity factor for two analytes in a
column provides a measure of how well the
column will separate the two.
• α is always greater than unity.
• Greater the selectivity factor, greater will be
the separation between the two components.
21. Principles of Chromatography
Raising
VS General increase in retention time
VM General decrease in retention time
µ Increases speed of separation.
• VS and VM can be altered by changing column
diameter and length for specific column packing.
• µ can be altered by changing the flowrate.
• All terms can be found by knowing how the
column was prepared.
22. All research in this field is aimed towards
maximum separation of components in minimum
time possible or in other words increasing the
efficiency of the column
Measure of column efficiency is given by
number of Theoretical Plates and Height
equivalent to theoretical plates (HETP)
Explained by Plate and Rate Theories
23. Plate Theory
Plate theory assumes that a column is
mathematically equivalent to a plate
column.
An equilibrium is established for the solute
between the mobile and stationary phase on
each plate.
It is a useful theory and can predict many
aspects of chromatographic performance.
24. Plates of fractionating column
• In a fractioning column
equilibrium is established
between the liquid and
gaseous phase at every
bubble cap plate.
• Likewise it is imagined that
in a chromatographic
column , solute equilibrium
is established between
stationary and mobile
phase at every imaginary
plate
25. Plate and Rate Theories
σ standard deviation σ2
/L variance per unit length.
L = length of column packing
L
H
H
L
N
N
H
2
platesofnumber
heightplate
σ
=
=
=
=
26. Plate Theory
The number of plates ( N ) can be determined
from the retention time and peak width.
It doesn’t matter what units (minutes or
seconds) are used as long as they are same.
27. Determination of N
The number of plates is calculated as:
N = 16 tR
W
This approach is taken because peaks evolve as
Gaussian-like shapes and can be treated statistically.
In essence, we are taking + 2 σ or 4 σ.
2
28. Determination of N
• We can measure the
width at half height.
• This insures that we
are well above
background noise and
away from any
detector sensitivity
limit problems.
29. Determination of N
Since the peak is Gaussian in nature, we end up with the
following modified formula.
N = 5.54 tR
W1/2
For a fixed length column, we can calculate an additional term
– h (or HETP)
h = height equivalent of a theoretical plate
= column length / N
2
31. Summary of Plate Theory
• Successfully accounts for the peak shapes and
rate of movement
• Does not account for the ‘mechanism’ causing
peak broadening
• No indication of other parameters’ effects
• No indication for adjusting experimental
parameters
32. Band/ Zone broadening
• In this example, we have materials with the
same elution time but different numbers of
plates
• Zone broadening is related to Mass Transfer
processes
33. Band Broadening
Band Broadening is a major problem because it effects the
resolution of solutes that have similar retention time. The
peak width increases with the square root of column length.
Therefore, we just cannot make a column longer to obtain a
‘better’ separation.
34. Rate theory
Plate theory neglects the concepts of solute diffusion
and flow paths which lead to band broadening.
Rate theory accounts for these and presumes band
broadening is caused due to:
• Slow equilibrium of solute between mobile and
stationary phases
• Time is required for solute molecules to diffuse from
the interior of these phase to there interface where
transfer occur
35. Theory of Band Broadening
van Deemter Equation
Theoretical studies of zone broadening in the 1950s by
Dutch chemical engineers led to the van Deemter
equation, which can be written in the form
H = B + CSu + Cmu
u
where
B – longitudinal diffusion
CS–mass transfer coefficient in mobile phase
CM-mass transfer coefficient in stationary phase
u– velocity of mobile phase
36. LONGITUDINAL DIFFUSION
Longitudinal diffusion term (B/u) depends upon
diffusion coefficient DM. Solute continuously
diffuses away from the concentrated center of its
zone.
The longer the solute is in the column, broadening
effect increases,
Zone of solute after short time on column
Zone of solute after longer time on column
Direction of travel
37. MASS TRANSFER TERM- CSu
Csu is
α thickness of the stationary phase film on the support particles
α the flow rate
1/ α diffusion coefficient DS of the solute in
the film
Slower rate of mass transfer increases plate height which is undesirable
38. MASS TRANSFER TERM CMU
α square of particle diameter of the packing
α square of column diameter
α flow rate
1/ α diffusion coefficient of analyte in the
mobile phase DM
Zone broadening or band broadening occurs due to
a) eddy diffusion- different path lengths passed by
solutes
b) diffusion of solute from one stream of mobile phase
to another
c) stagnant or static pools of solvent formed within
stationary phase
39.
40. Effect of flow rate (µ)
• Broadening effects may be minimized by careful
control of the flow rate.
• Generally, the amount of broadening increases as
the flow rate decreases.
• Broadening α 1 / µ
• Sufficient time must be allowed for the solute to
equilibrate between the two phases. For a given
separation there will be some optimum flow rate.
• This optimum flow rate is found experimentally.
41.
42.
43. Methods for Reducing Band Broadening
• Small packing diameter (of stationary
phase)
• Small column diameter
• For liquid stationary phase- thickness of
the layer should be minimized
• Optimum flow-rate of mobile phase
• Optimum temperature
• Variation in solvent composition
47. Liquid chromatography
• At first, LC relied on
irregular packing.
Now the packing are
pretty good so the
CSu term is very low.
• The B/u and CMu
terms are low
because liquids
diffuse much more
slowly than gases
48. Column Resolution
Resolution R, of a column provides a
quantitative measure of its ability to
separate two analytes.
Resolution of 1.5 gives almost complete peak
separation
The smaller the HETP or larger the N, the
higher the resolving power of the column.
52. FACTORS FOR INCREASING RESOLUTION
1. Increase column length
2. Decrease column diameter
3. Decrease flow-rate
4. Pack column uniformly
5. Use uniform stationary phase (packing material)
6. Decrease sample size
7. Select proper stationary phase
8. Select proper mobile phase
9. Use proper pressure
10. Use gradient elution
53. Unsymmetrical bands
Often the actual bands observed are not
symmetrical Gaussian curves but rather show
one of following behaviours.
Careful adjustment of the operational
parameters, especially the size of sample may
correct these problems.
They may also be attributed to poor column
packing or sample injection.