Download S07 Phytoanalysis HPLC Part1

What Is HPLC?
Basic Principles
LAAQ-B-LC001B
1
Invention of Chromatography by
M. Tswett
Ether
Chlorophyll
Chromatography
Colors
CaCO3
LAAQ-B-LC001B
2
Comparing Chromatography to the
Flow of a River...
Light leaf
Heavy stone
Water flow
Base
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3
Mobile Phase / Stationary Phase

Mobile
phase
Strong
Stationary
phase
LAAQ-B-LC001B
Weak
A site in which a moving
phase (mobile phase) and
a non-moving phase
(stationary phase) make
contact via an interface
that is set up.
 The affinity with the mobile
phase and stationary
phase varies with the
solute.  Separation
occurs due to differences
in the speed of motion.
4
Chromato-graphy / -graph / -gram /
-grapher

Chromatography:
 Chromatograph:
 Chromatogram:
 Chromatographer:
LAAQ-B-LC001B
Analytical technique
Instrument
Obtained “picture”
Person
5
Three States of Matter and
Chromatography Types
Mobile phase
Gas
Liquid
Gas
chromatography
Liquid
chromatography
Solid
Gas
Stationary
phase
Liquid
Solid
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6
Liquid Chromatography

Chromatography in which the mobile phase
is a liquid.
 The
liquid used as the mobile phase is
called the “eluent”.

The stationary phase is usually a solid or a
liquid.
 In general, it is possible to analyze any
substance that can be stably dissolved in
the mobile phase.
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7
Interaction Between Solutes, Stationary
Phase, and Mobile Phase

Differences in the interactions between the solutes and
stationary and mobile phases enable separation.
Solute
Degree of adsorption,
solubility, ionicity, etc.
Stationary
phase
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Mobile phase
8
Column Chromatography and
Planar Chromatography
Separation column
Paper or a
substrate coated
with particles
Packing material
Column Chromatography
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Paper Chromatography
Thin Layer Chromatography (TLC)
9
Separation Process and Chromatogram
Output
concentration
for Column Chromatography
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Chromatogram
Time
10
Intensity of detector signal
Chromatogram
tR
Peak
t0
tR : Retention time
t0 : Non-retention time
h
A
A : Peak area
h : Peak height
Time
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11
From Liquid Chromatography to High
Performance Liquid Chromatography

Higher degree of separation!
 Refinement of packing material (3 to 10 µm)
 Reduction of analysis time!
 Delivery of eluent by pump
 Demand for special equipment that can
withstand high pressures
The arrival of high performance liquid chromatography!
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12
Flow Channel Diagram for High
Performance Liquid Chromatograph
Detector
Column
Pump
Eluent
(mobile phase)
Column oven
(thermostatic
column chamber)
Sample injection unit
(injector)
Drain
Data processor
Degasser
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13
Advantages of High Performance
Liquid Chromatography

High separation capacity, enabling the batch
analysis of multiple components
 Superior quantitative capability and reproducibility
 Moderate analytical conditions

Unlike GC, the sample does not need to be vaporized.

Generally high sensitivity
 Low sample consumption
 Easy preparative separation and purification of
samples
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14
Fields in Which High Performance
Liquid Chromatography Is Used

Biogenic substances


Sugars, lipids, nucleic
acids, amino acids,
proteins, peptides, steroids,
amines, etc.



Medical products

Food products
Environmental
samples

Drugs, antibiotics, etc.


Inorganic ions
Hazardous organic
substances, etc.
Organic industrial
products

LAAQ-B-LC001B
Vitamins, food additives,
sugars, organic acids,
amino acids, etc.
Synthetic polymers,
additives, surfactants, etc.
15
HPLC Hardware: Part 1
Solvent Delivery System,
Degasser, Sample Injection Unit,
Column Oven
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Flow Channel Diagram for HPLC
Detector
Column
Pump
Eluent
(mobile phase)
Column Oven
(thermostatic
column chamber)
Sample injection unit
(injector)
Drain
Data processor
Degasser
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Solvent Delivery Pump

Performance Requirements
 Capacity
to withstand high load pressures.
 Pulsations that accompany pressure
fluctuations are small.
 Flow rate does not fluctuate.
 Solvent replacement is easy.
 The flow rate setting range is wide and the
flow rate is accurate.
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Solvent Delivery Pump:
Representative Pumping Methods
Syringe pump
 Plunger pump
 Diaphragm pump

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Solvent Delivery Pump:
Schematic Diagram of Plunger Pump
Motor and cam
Pump head
Check
valves
Plunger
Plunger seal
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10 -100µL
20
Solvent Delivery Pump:
Single Plunger Type
Check valves
Plunger head
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21
Solvent Delivery Pump:
Dual Plunger Type
Check valves
Plunger heads
Type
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Type
22
Gradient System

Isocratic system
 Constant

eluent composition
Gradient system
 Varying
eluent composition
 HPGE
(High Pressure Gradient)
 LPGE (Low Pressure Gradient)
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23
Aim of Gradient System (1)

In isocratic mode
CH3OH / H2O = 6 / 4
Long analysis time!!
Poor
separation!!
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(Column: ODS type)
CH3OH / H2O = 8 / 2
24
Aim of Gradient System (2)
If the eluent composition is changed gradually during
analysis...
Concentration of methanol in eluent

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95%
30%
25
High- / Low-Pressure Gradient System
Low-pressure
gradient unit
Mixer
High-pressure gradient
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Mixer
Low-pressure gradient
26
Advantages and Disadvantages of
High- / Low-Pressure Gradient Systems

High-pressure gradient system
 High
gradient accuracy
 Complex system configuration (multiple
pumps required)

Low-pressure gradient system
 Simple
system configuration
 Degasser required
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27
Degasser

Problems caused by dissolved air in the eluent
Unstable delivery by pump
 More noise and large baseline drift in detector cell

In order to avoid these problems, the eluent
must be degassed.
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Online Degasser
Regulator
Helium
cylinder
Polymeric film tube
Vacuum chamber
To pump
To pump
To draft
Drain valve
Eluent container
Helium purge method
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Eluent container
Gas-liquid separation membrane method
29
Sample Injection Unit (Injector)

Performance Requirements
 No
sample remaining in unit
 Minimal broadening of sample band
 Free adjustment of injection volume
 Minimal loss
 Superior durability and pressure resistance
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30
Manual Injector
From pump
To column
LOAD position
From pump
INJECT position
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To column
31
Manual Injector:
Operating Principle of Sample Injection
From pump
Loop
Loop
From pump
To column
To column
LOAD
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INJECT
32
Manual Injector:
Injection Method

Syringe measurement method
 It
is desirable that no more than half the loop
volume is injected.

Loop measurement method
 It
is desirable that at least 3 times the loop
volume is injected.
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33
Autosampler
(Pressure Injection Method)
From pump
To column
From pump
To column
Sample Loop
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LOAD
INJECT
34
Autosampler
(Total-Volume Injection Method)
From pump
To column
From pump
To column
Needle
Sample vial
LOAD
INJECT
Measuring pump
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35
Column Oven
Air circulation heating type
 Block heating type

 Aluminum

block heater
Insulated column jacket type
 Water
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bath
36
Tubing and Preparation for
Solvent Delivery
Prior to Analysis
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Tubing

Material
Stainless steel (SUS)
 PEEK (polyether
ether ketone)
 Fluororesin


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O.D. (outer diameter)


1.6 mm
I.D. (inner diameter)
0.1 mm
 0.3 mm
 0.5 mm
 0.8 mm etc.

38
Connectors

Male nut (SUS)
Ferrule (SUS)


Sealing possible up to 40
MPa
Ferrule
Male nut
Male nut (PEEK)


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Can be connected without
any tools
Resists pressures of up to
approx. 25 MPa
Male nut (PEEK)
39
Dead Volume
(Extra-column volume)

Dead volume can cause peaks broadening.
Male nut
Dead volume
Tube
Excellent connection
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Poor connection
40
Mobile Phase

Water


“Ultrapure water” can be
used with confidence.
Commercial “distilled
water for HPLC” is also
acceptable.

Organic Solvent



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HPLC-grade solvent can
be used with confidence.
Special-grade solvent is
acceptable depending on
the detection conditions.
Care is required regarding
solvents containing
stabilizers (e.g.,
tetrahydrofuran and
chloroform)
41
Replacement of Eluent

Mutually insoluble solvents
must not be exchanged
directly.
Water
2-Propanol
Hexane
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
Aqueous solutions containing
salt and organic solvents
must not be exchanged
directly.
Buffer solution
Water
Water-soluble
organic solvent
42
Mixing, Filtration, and Offline
Degassing of the Eluent
Decompression
by aspirator
Membrane filter with pore
size of approx. 0.45 µm
Decompression
by aspirator
Ultrasonic
cleaning unit
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43
Reversed Phase Chromatography
Part 1
Basic Principles
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44
Polarity of Substances


Polarity


Property of a substance
whereby the positions of the
electrons give rise to
positive and negative poles
Water: Polar
Methane: Nonpolar
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H

O
C
H

–
H
H
H
Methane
+
Miscibility of solvents
H
Water
Solvents of similar
polarities can be easily
dissolved together.
Polar and nonpolar
molecules have a similar
relationship to that of water
and oil.
H
O
H C C
–
O
H
Acetic acid
45
Nonpolar (Hydrophobic) Functional Groups
and Polar (Hydrophilic) Functional Groups

Nonpolar Functional
Groups

-(CH2)nCH3


Polar Functional
Groups

Alkyl groups
-C6H5


-COOH


Phenyl groups
-NH2


Amino groups
-OH

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Carboxyl groups
Hydroxyl groups
46
Partition Chromatography
A liquid (or a substance regarded as a
liquid) is used as the stationary phase,
and the solute is separated according to
whether it dissolves more readily in the
stationary or mobile phase.
 Liquid-liquid chromatography

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47
Normal Phase / Reversed Phase
Stationary
phase
Mobile phase
Normal
phase
High polarity
Low polarity
(hydrophilic)
(hydrophobic)
Reversed
phase
Low polarity
High polarity
(hydrophobic)
(hydrophilic)
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48
Reversed Phase Chromatography

Stationary phase: Low polarity
 Octadecyl

group-bonded silical gel (ODS)
Mobile phase: High polarity
 Water,
methanol, acetonitrile
 Salt is sometimes added.
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49
Separation Column for Reversed
Phase Chromatography

C18 (ODS) type
 C8 (octyl) type
 C4 (butyl) type
Si
-O-Si

Phenyl type
 TMS type
 Cyano type
CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2
CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
C18 (ODS)
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Effect of Chain Length of
Stationary Phase
C8
Medium
C18 (ODS)
Strong
C4
Weak
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Hydrophobic Interaction
H2O
H2O
H2O
H2O
H2O
H2O
H2O
Nonpolar solute
H2O
H2O
If a nonpolar
H2O
substance is added...
H2O
H2O
H2O
H2O
H2O
H2O
Nonpolar solute
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H2O
H2O
H2O
…the network is broken and...
Network of hydrogen bonds
H2O
H2O
Nonpolar stationary phase
…the nonpolar substance
is pushed to a nonpolar
location.
52
Relationship Between Retention
Time and Polarity
OH
C18 (ODS)
Weak
Strong
CH3
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Basic Settings for Eluent Used in
Reversed Phase Mode

Water (buffer solution) + water-soluble organic
solvent
Water-soluble organic solvent: Methanol
Acetonitrile
Tetrahydrofuran etc.
 The mixing ratio of the water (buffer solution) and
organic solvent has the greatest influence on
separation.
 If a buffer solution is used, its pH value is an
important separation parameter.

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54
Difference in Solute Retention Strengths
for Water and Water-Soluble Organic
Solvents
Tightly packed network
H2O
H2O
H2O
H2O
H2O
Loose network
CH3OH
H2O
H2O
CH3OH
CH3OH
CH3OH
CH3OH
Nonpolar solute
CH3OH
CH3OH
Nonpolar solute
Nonpolar stationary phase
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55
Relationship between Polarity of Eluent and
Retention Time in Reversed Phase Mode
Eluent: Methanol / Water
60/40
70/30
80/20
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56
Chromatogram Parameters
Methods for Expressing Separation
and Column Performance
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57
Theory of Chromatography
1.) Typical response obtained by chromatography (i.e., a chromatogram):
chromatogram - concentration versus elution time
Wh
Wb
Inject
Where:
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tR = retention time
tM = void time
Wb = baseline width of the peak in time units
Wh = half-height width of the peak in time units
Note: The separation of solutes in chromatography depends on two factors:
(a) a difference in the retention of solutes (i.e., a difference in their time or volume of
elution
(b) a sufficiently narrow width of the solute peaks (i.e, good efficiency for the separation
system)
Peak width & peak position
determine separation of peaks
A similar plot can be made in terms of elution volume instead of elution time. If volumes
are used, the volume of the mobile phase that it takes to elute a peak off of the column is
referred to as the retention volume (VR) and the amount of mobile phase that it takes to
elute a non-retained component is referred to as the void volume (VM).
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2.) Solute Retention:
A solute’s retention time or retention volume in chromatography is directly related to the
strength of the solute’s interaction with the mobile and stationary phases.
Retention on a given column pertain to the particulars of that system:
- size of the column
- flow rate of the mobile phase
Capacity factor (k’): more universal measure of retention, determined from tR or VR.
k’ = (tR –tM)/tM
or
k’ = (VR –VM)/VM
capacity factor is useful for comparing results obtained on different systems since it is
independent on column length and flow-rate.
LAAQ-B-LC001B
The value of the capacity factor is useful in understanding the retention mechanisms for a
solute, since the fundamental definition of k’ is:
k’ =
moles Astationary phase
moles Amobile phase
k’ is directly related to the strength of the interaction between a solute with the stationary
and mobile phases.
Moles Astationary phase and moles Amobile phase represents the amount of solute present in each
phase at equilibrium.
Equilibrium is achieved or approached at the center of a chromatographic peak.
When k' is # 1.0, separation is poor
When k' is > 30, separation is slow
When k' is = 2-10, separation is optimum
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A simple example relating k’ to the interactions of a solute in a column is illustrated for
partition chromatography:
KD
A (mobile phase)
A (stationary phase)
where: KD = equilibrium constant for the distribution of A between the mobile
phase and stationary phase
Assuming local equilibrium at the center of the chromatographic peak:
k’ =
[A]stationary phase Volumestationary phase
[A]mobile phase Volumemobile phase
k’ = KD
Volumestationary phase
Volumemobile phase
As KD increases, interaction of the solute with the stationary phase becomes more
favorable and the solute’s retention (k’) increases
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k’ = KD
Volumestationary phase
Volumemobile phase
Separation between two solutes requires different KD’s for their
interactions with the mobile and stationary phases
since
DG = -RT ln KD
peak separation also represents different changes in free energy
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3.) Efficiency:
Efficiency is related experimentally to a solute’s peak width.
- an efficient system will produce narrow peaks
- narrow peaks  smaller difference in interactions in order to separate two solutes
Efficiency is related theoretically to the various kinetic processes that are involved in
solute retention and transport in the column
- determine the width or standard deviation (s) of peaks
Estimate s from peak widths,
assuming Gaussian shaped peak:
Wh
Wb = 4s
Wh = 2.354s
Dependent on the amount of time that a solute spends in the column (k’ or tR)
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Number of theoretical plates (N): compare efficiencies of a system for solutes that have
different retention times
N = (tR/s)2
or for a Gaussian shaped peak
N = 16 (tR/Wb)2
N = 5.54 (tR/Wh)2
The larger the value of N is for a column, the better the column will be able to separate
two compounds.
- the better the ability to resolve solutes that have small differences in retention
- N is independent of solute retention
- N is dependent on the length of the column
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Plate height or height equivalent of a theoretical plate (H or HETP): compare efficiencies of
columns with different lengths:
H = L/N
where: L = column length
N = number of theoretical plates for the column
Note: H simply gives the length of the column that corresponds to one theoretical plate
H can be also used to relate various chromatographic parameters (e.g., flow rate, particle size,
etc.) to the kinetic processes that give rise to peak broadening:
Why Do Bands Spread?
a. Eddy diffusion
b. Mobile phase mass transfer
c. Stagnant mobile phase mass transfer
d. Stationary phase mass transfer
e. Longitudinal diffusion
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a.) Eddy diffusion – a process that leads to peak (band) broadening due to the presence
of multiple flow paths through a packed column.
As solute molecules travel through the column,
some arrive at the end sooner then others simply
due to the different path traveled around the
support particles in the column that result in
different travel distances.
Longer path arrives at end of column after (1).
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b.) Mobile phase mass transfer – a process of peak broadening caused by the
presence of different flow profile within channels or
between particles of the support in the column.
A solute in the center of the channel
moves more quickly than solute at the
edges, it will tend to reach the end of
the channel first leading to bandbroadening
The degree of band-broadening due to eddy diffusion and mobile phase
mass transfer depends mainly on:
1) the size of the packing material
2) the diffusion rate of the solute
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c.) Stagnant mobile phase mass transfer – band-broadening due to differences in the
rate of diffusion of the solute molecules between the
mobile phase outside the pores of the support
(flowing mobile phase) to the mobile phase within
the pores of the support (stagnant mobile phase).
Since a solute does not travel down
the column when it is in the stagnant
mobile phase, it spends a longer time
in the column than solute that
remains in the flowing mobile phase.
The degree of band-broadening due to stagnant mobile phase mass
transfer depends on:
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1) the size, shape and pore structure of the packing material
2) the diffusion and retention of the solute
3) the flow-rate of the solute through the column
d.) Stationary phase mass transfer – band-broadening due to the movement of solute
between the stagnant phase and the stationary phase.
Since different solute molecules
spend different lengths of time in the
stationary phase, they also spend
different amounts of time on the
column, giving rise to bandbroadening.
The degree of band-broadening due to stationary phase mass transfer
depends on:
LAAQ-B-LC001B
1) the retention and diffusion of the solute
2) the flow-rate of the solute through the column
3) the kinetics of interaction between the solute and the
stationary phase
e.) Longitudinal diffusion – band-broadening due to the diffusion of the solute along the
length of the column in the flowing mobile phase.
The degree of band-broadening due
to longitudinal diffusion depends on:
1) the diffusion of the solute
2) the flow-rate of the solute through
the column
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Van Deemter equation: relates flow-rate or linear velocity to H:
H = A + B/m + Cm
where:
m = linear velocity (flow-rate x Vm/L)
H = total plate height of the column
A = constant representing eddy diffusion &
mobile phase mass transfer
B = constant representing longitudinal diffusion
C = constant representing stagnant mobile phase
& stationary phase mass transfer
One use of plate height (H) is to relate these kinetic process to band broadening to a
parameter of the chromatographic system (e.g., flow-rate).
This relationship is used to predict what the resulting effect would be of varying this
parameter on the overall efficiency of the chromatographic system.
Number of theoretical plates(N)
LAAQ-B-LC001B
(N) = 5.54 (tR/Wh)2
H = L/N
peak width (Wh)
Plot of van Deemter equation shows how H changes with the linear velocity (flow-rate) of
the mobile phase
m optimum
Optimum linear velocity (mopt) - where H has a minimum value and the point of maximum
column efficiency:
mopt = rB/C
mopt is easy to achieve for gas chromatography, but is usually too small for liquid
chromatography requiring flow-rates higher than optimal to separate compounds
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4.) Measures of Solute Separation:
separation factor (a) – parameter used to describe how well two solutes are separated by
a chromatographic system:
a = k’2/k’1
k’ = (tR –tM)/tM
where:
k’1 = the capacity factor of the first solute
k’2 = the capacity factor of the second solute,
with k’2 $ k’1
A value of a $1.1 is usually indicative of a good separation
Does not consider the effect of column efficiency or peak widths, only retention.
LAAQ-B-LC001B
resolution (RS) – resolution between two peaks is a second measure of how well two
peaks are separated:
RS =
tr2 – tr1
(Wb2 + Wb1)/2
where:
tr1, Wb1 = retention time and baseline width for the
first eluting peak
tr2, Wb2 = retention time and baseline width for the
second eluting peak
Rs is preferred over a since both
retention (tr) and column efficiency
(Wb) are considered in defining
peak separation.
Rs $ 1.5 represents baseline
resolution, or complete separation
of two neighboring solutes  ideal
case.
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Rs $ 1.0 considered adequate for
most separations.
Strength of detector signal
Retention Factor, k
t R  t0
k
t0
tR
t0
tR: Retention time
t0: Non-retention time
Time
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76
Theoretical Plate Number, N
tR
N  16
W
H
W1/2
H1/2
W
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2
tR
 5.54
W1/ 2
 2
tR  H
Area
2
2
77
Evaluation of Column Efficiency Based on
Theoretical Plate Number

If the retention times are
the same, the peak width
is smaller for the one with
the larger theoretical plate
number.
N: Large

If the peak width is the
same, the retention time is
longer for the one with the
larger theoretical plate
number.
N: Small
N: Large
N: Small
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78
Separation Factor, α

Separation factor: Ratio of k’s of two peaks
k1
k2
k2
a
k1
( k 2  k1 )
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79
Resolution, RS
tR1
tR2
RS 
W1/2h,1
W1/2h,2
W1
LAAQ-B-LC001B
h1/2
t R 2  t R1
1
(W1  W2 )
2
t R 2  t R1
 1.18 
W1/ 2 h ,1  W1/ 2 h, 2
W2
80
Resolution Required for Complete
Separation
(tR2 - tR1)
(tR2 - tR1)
W1 W2
W1 W2
tR2 - tR1 = W1 = W2
tR2 - tR1 = W1 = W2
RS = 1
LAAQ-B-LC001B
If the peaks are isosceles triangles,
they are completely separated.
RS = 1
If the peaks are Gaussian distributions,
RS > 1.5 is necessary for complete separation.
81
Relationship Between Resolution
and Other Parameters


The resolution is a
function of the
separation factor, the
theoretical plate
number, and the
retention factor.
The separation can be
improved by improving
these 3 parameters!
LAAQ-B-LC001B
RS 
tR 2  tR1
1
(W1  W2 )
2
a 1
1

N
a
4
k’2
k’2  1
82

Increasing the capacity
factor improves
separation!
 A capacity factor of
around 3 to 10 is
appropriate. Exceeding
this just increases the
analysis time.
Contribution ratio for resolution
Contribution of Capacity Factor to
Resolution
1.0
0.8
0.6
0.4
0.2
0.0
0
5
10
15
20
Capacity factor
LAAQ-B-LC001B
83

The resolution
increases in
proportion to the
square root of the
theoretical plate
number.
Contribution factor for resolution
Contribution of Theoretical Plate
Number to Resolution
2.0
1.0
0.0
0
10000 20000 30000
Theoretical plate number
LAAQ-B-LC001B
84
To Improve Separation...
Before
adjustment
k’ increased
N increased
a increased
LAAQ-B-LC001B
Eluent replaced with one
of lower elution strength.
Column replaced with one of
superior performance.
Column lengthened.
Column (packing material) replaced.
Eluent composition changed.
Column temperature changed.
85
pH Buffer Solution Used for Eluent
Selection and Preparation of
Buffer Solution
LAAQ-B-LC001B
86
Acid Dissociation Equilibrium
H+
If an acid is added...
...the equilibrium shifts to
the left to offset the
increase in H+.
A- + H+
HA
If an alkali is
added...
…the equilibrium shifts
to the right to offset the
decrease in H+.
LAAQ-B-LC001B
OH-
The equilibrium always shifts
in a way that offsets changes.
87
Acid Dissociation Constant and
pH-Based Abundance Ratio
HA
+
1.0
H+
The acid dissociation constant, Ka,
is defined as follows:


[A ][ H ]
Ka 
[HA ]
0.8
0.6
0.4
[A  ]
pH  pK a  log
[HA ]
0.2
0.0
1
 pH   log[ H ] 


 pK   log K 
a 
 a

LAAQ-B-LC001B
CH3COO-
CH3COOH
Abundance ratio
A-
2
3
4
5
6
7
8
9
pH
pKa
Relationship Between Abundance Ratio
and pH Value of Acetic Acid and Acetic Acid Ions
88
Preparing pH Buffer Solution

Use a weak acid with a pKa value close to the
desired pH value.


Example: Preparing a buffer solution for a pH value of
around 4.8.
 Use acetic acid, which has a pKa value of 4.8.
Make the concentrations of HA and A- roughly
equal.
 Mix an acid with its salt.

Example: Mix acetic acid and sodium acetate so that they
have the same molar concentration.
LAAQ-B-LC001B
89
Buffer Solutions Used for HPLC Eluent

Requirements

Commonly Used Acids
 Phosphoric acid
High buffering power at
 pKa 2.1, 7.2, 12.3
prescribed pH.
 Acetic acid
 Does not adversely
 pKa 4.8
affect detection.
 Citric acid
 Does not damage
 pKa 3.1, 4.8, 6.4
column or equipment.
 Concentration
 Inexpensive.
 If only to adjust pH, 10
mmol/L is sufficient.

LAAQ-B-LC001B
90
Characteristics of Phosphate
Buffer Solution

Advantages

Three dissociation
states
(pKa 2.1, 7.2, 12.3)

Possible to prepare
buffer solutions of
various pH values.

Disadvantages

No volatility

Difficult to use for
LCMS or evaporative
light scattering
detection.
No UV absorption
 Inexpensive

LAAQ-B-LC001B
91
Reversed Phase Chromatography
Part 2
Consideration of Analytical
Conditions
LAAQ-B-LC001B
92
Guidelines for Setting Mobile Phase
Conditions (1)
Neutral (Nonionic) Substances

Eluent Composition
 Water
/ acetonitrile
 Water / methanol

Separation Adjustment
 Changing
the mixing ratio of the water and
organic solvent
 Changing the type of organic solvent
LAAQ-B-LC001B
93
pH of Eluent and Retention of Ionic
Solutes
COOH
Acidic
Increased
hydrophobicity
pH of eluent
COO
Alkaline
Increased
hydrophilicity
+
H
LAAQ-B-LC001B
94
Guidelines for Setting Mobile Phase
Conditions (2)
Acidic (Anionic) Substances

Eluent Composition
Acidic buffer solution / acetonitrile
 Acidic buffer solution / methanol

Increase retention strength by making
the eluent acidic and suppressing
ionization!
LAAQ-B-LC001B
95
Analysis of Basic Substances (1)
Problems Encountered with Alkaline Eluents
N+
H
N
OH
With alkaline eluents, although the
ionization of basic substances is
suppressed, and the retention
strength increases...
Si
O
OH
Si
OH
OH
OH
LAAQ-B-LC001B
…silica gel dissolves in alkalis,
so the packing material
deteriorates rapidly.
OH
96
Analysis of Basic Substances (2)
Influence of Residual Silanol Groups
Basic substances interact with the
residual silanol groups, causing
delayed elution and tailing.
Si
O
Si
-O-Si-O
Residual silanol group
O
Si
LAAQ-B-LC001B
N+
H
97
Analysis of Basic Substances (3)
Addition of Sodium Perchlorate
ClO4
N+
H
Ion pair
Si
O
Si
LAAQ-B-LC001B
Basic substances form ion pairs with perchlorate
ions, thereby balancing the charge and
increasing the retention strength.
98
Guidelines for Setting Mobile Phase
Conditions (3)
Basic Substances (Cationic Substances)

Eluent Composition
Acidic buffer solution containing anions with a low
charge density (e.g., perchlorate ions) / acetonitrile
 As above / methanol

Making eluent acidic
 Suppresses dissociation of residual silanol groups
 Prevents tailing!
Adding perchlorate ions
 Forms ion pairs  Increases retention strength!
 Suppresses tailing!
LAAQ-B-LC001B
99
Reversed Phase Ion Pair
Chromatography

Increase the retention strength by adding an ion pair
reagent with the opposite charge to the target
substance into the eluent.
Ion pair formation
Ion exchange-like effect
LAAQ-B-LC001B
Basic Substance
Ion pair formation
Ion exchange-like effect
Acidic Substance
100
Representative Ion Pair Reagents

Anionic Compounds
 Tetra-n-butylammonium

hydroxide (TBA)
Cationic Compounds
 Pentanesulfonic
acid sodium salt (C5)
 Hexanesulfonic acid sodium salt (C6)
 Heptanesulfonic acid sodium salt (C7)
 Octanesulfonic acid sodium salt (C8)
LAAQ-B-LC001B
101
Points to Note Concerning the Use
of Ion Pairs

Selection of Ion Pair Reagent


pH of Eluent


The retention strength changes according to whether or not
ionization takes place.
Concentration of Ion Pair Reagent


In general, the retention strength increases with the length of
the alkyl chain.
In general, the retention strength increases with the ion pair
concentration, but there is an upper limit.
Proportion of Organic Solvent in Eluent

LAAQ-B-LC001B
Optimize the separation conditions by considering the type and
concentration of the ion pair reagent.
102
HPLC Separation Modes
Separation Modes Other Than
Reversed Phase Chromatography
LAAQ-B-LC001B
103
HPLC Separation Modes
Adsorption (liquid-solid) chromatography
 Partition (liquid-liquid) chromatography

 Normal
phase partition chromatography
 Reversed phase partition chromatography
Ion exchange chromatography
 Size exclusion chromatography

LAAQ-B-LC001B
104
Adsorption Chromatography
A solid such as silica gel is used as the
stationary phase, and differences, mainly
in the degree of adsorption to its surface,
are used to separate the solutes.
 Liquid-solid chromatography
 The retention strength increases with the
hydrophilicity of the solute.

LAAQ-B-LC001B
105
Partition Chromatography
A liquid (or a substance regarded as a
liquid) is used as the stationary phase, and
the solute is separated according to
whether it dissolves more readily in the
stationary or mobile phase.
 Liquid-liquid chromatography

LAAQ-B-LC001B
106
Normal Phase and Reversed Phase
Solid phase
Mobile phase
Normal
phase
High polarity
(hydrophilic)
Low polarity
(hydrophobic)
Reversed
phase
Low polarity
(hydrophobic)
High polarity
(hydrophilic)
LAAQ-B-LC001B
107
Normal Phase (Partition)
Chromatography


Partition chromatography in which the
stationary phase has a high polarity
(hydrophilic) and the mobile phase has a
low polarity (hydrophobic)
Essentially based on the same separation
mechanism as adsorption chromatography
in which the stationary phase has a
hydrophilic base, such as silica gel
LAAQ-B-LC001B
108
Invention of Chromatography by
M. Tswett
Ether
Chlorophyll
Chromatography
Colors
CaCO3
LAAQ-B-LC001B
109
Stationary Phase and Mobile Phase Used
in Normal Phase Mode

Stationary Phase
Silica gel: -Si-OH
 Cyano type: -Si-CH2CH2CH2CN
 Amino type: -Si-CH2CH2CH2NH2
 Diol type: -Si-CH2CH2CH2OCH(OH)-CH2OH


Mobile Phase
Basic solvents: Aliphatic hydrocarbons,
aromatic hydrocarbons, etc.
 Additional solvents: Alcohols, ethers, etc.

LAAQ-B-LC001B
110
Relationship between Hydrogen Bonding
and Retention Time in Normal Phase Mode
SiOH
Strong
HO
SiOH
Weak
Very weak
OH
Steric hindrance
LAAQ-B-LC001B
111
Relationship Between Eluent Polarity and
Retention Time in Normal Phase Mode
Eluent: Hexane/methanol
100/0
98/2
95/5
LAAQ-B-LC001B
112
Comparison of Normal Phase and
Reversed Phase

Normal Phase




LAAQ-B-LC001B
Effective for separation
of structural isomers
Offers separation
selectivity not available
with reversed phase
Stabilizes slowly and is
prone to fluctuations in
retention time
Eluents are expensive

Reversed Phase





Wide range of applications
Effective for separation of
homologs
Stationary phase has long
service life
Stabilizes quickly
Eluents are inexpensive
and easy to use
113
Ion Exchange Chromatography
R
Anion exchange
N+ R
R
Cation exchange
SO3-
++++
+
+
++++
Electrostatic interaction
(Coulomb force)
LAAQ-B-LC001B
114
Stationary Phase Used in Ion
Exchange Mode

Base Material
Resin is often used.
 Silica gel is also used.


Cation Exchange Column
Strong cation exchange
 Week cation exchange


(SCX)
(WCX)
-SO3-COO-
(SAX)
(WAX)
-NR3+
-NHR2+
Anion Exchange Column
Strong anion exchange
 Week anion exchange

LAAQ-B-LC001B
115
Dependence of Exchange Capacity of Ion
Exchanger on pH of Eluent
Strongly basic
anion exchanger
Weakly acidic
cation exchanger
0
7
pH
Cation exchange mode
LAAQ-B-LC001B
14
Exchange capacity
Exchange capacity
Strongly acidic
cation exchanger
Weakly basic
anion exchanger
0
7
pH
14
Anion exchange mode
116
Relationship between Retention Time and
Salt Concentration of Eluent in Ion
Exchange Mode
Resin
Resin
Resin
The exchange groups
are in equilibrium with
anions in the eluent.
An eluent ion is
driven away
and a solute ion
is adsorbed.
The solute ion is driven
away by an eluent ion
and is adsorbed by the
next exchange group.
Solute ions and eluent ions compete for ion exchange groups.
If
the salt concentration of the eluent increases, the solutes are eluted sooner.
LAAQ-B-LC001B
117
Ion Exclusion Chromatography
H+
H+
H+
Strong acid ions are repelled by
charge and cannot enter the pore.
LAAQ-B-LC001B
Depending on the level of dissociation,
some weak acid ions can enter the pore.
118
Size Exclusion Chromatography


Separation is based on the size (bulkiness)
of molecules.
The name varies with the application field!
 Size
Exclusion Chromatography (SEC)
 Gel Permeation Chromatography (GPC)
 Chemical
industry fields, synthetic polymers,
nonaqueous systems
 Gel
Filtration Chromatography (GFC)
 Biochemical
fields, biological macromolecules,
aqueous systems
LAAQ-B-LC001B
119
Principle of Size Exclusion Mode
The size of the solute molecules
determines whether or not they can
enter the pores.
Packing
material
LAAQ-B-LC001B
120
Relationship Between Molecular Weight and
Retention Time in Size Exclusion Mode
Molecular weight
(logarithmic axis)
Exclusion limit
Permeability limit
Elution capacity
LAAQ-B-LC001B
121
Creating a Molecular Weight
Calibration Curve
Molecular weight
(logarithmic axis)
For separation of large molecular weights
For wide-range separation
(mix gel)
Elution capacity
For separation of small molecular weights
LAAQ-B-LC001B
122
Calculating Molecular Weights
Chromatogram

Various Average
Molecular Weights


Calibration curve


Retention time
LAAQ-B-LC001B
Mn: Number-average
molecular weight
Mw: Weight-average
molecular weight
Mz: Z-average molecular
weight, etc.
Molecular weights and
molecular weight
distributions are calculated
using special calculation
software.
123
Guidelines for Selecting Separation Mode (1)
Required Information
Soluble solvent
 Molecular weight
 Structural formula and chemical
properties

 Do
the substances ionize?
 Is there UV absorption or fluorescence?
 Is derivatization possible? etc.
LAAQ-B-LC001B
124
Guidelines for Selecting Separation Mode (2)
Basic Policy


Reversed phase mode using an ODS column
is the first choice!
Exceptions
Large molecular weight (> 2,000)  Size exclusion
 Optical isomers  Chiral column
 Stereoisomers, positional isomers  Normal phase /
adsorption
 Inorganic ions  Ion chromatography
 Sugars, amino acids, short-chain fatty acids
 Special column

LAAQ-B-LC001B
125
HPLC Hardware: Part 2
Detectors and Their Ranges of Application
LAAQ-B-LC001B
126
Detection Condition Requirements

Sensitivity
 The
detector must have the appropriate level of
sensitivity.

Selectivity
 The
detector must be able to detect the target
substance without, if possible, detecting other
substances.


Adaptability to separation conditions
Operability, etc.
LAAQ-B-LC001B
127
Representative HPLC Detectors








LAAQ-B-LC001B
UV-VIS absorbance detector
Photodiode array-type UV-VIS absorbance
detector
Fluorescence detector
Refractive index detector
Evaporative light scattering detector
Electrical conductivity detector
Electrochemical detector
Mass spectrometer
128
UV-VIS Absorbance Detector
Ein
Eout
A
C: Concentration
Detection cell
l
A = e·C·l = –log (Eout / Ein)
C
(A: absorbance, E: absorption coefficient)
LAAQ-B-LC001B
129
Optical System of UV-VIS
Absorbance Detector
Grating
l
Sample cell
Ein
Eout
Photodiode
Ein
Ein
Photodiode
Reference cell
D2 / W lamp
LAAQ-B-LC001B
130
Spectrum and Selection of
Detection Wavelength
The longer wavelength
is more selective.
200
LAAQ-B-LC001B
250
300
Wavelength [nm]
350
131
Optical System of Photodiode
Array Detector
Sample cell
Grating
A single photodiode
measures the absorbance for
the corresponding wavelength
at a resolution of approx. 1 nm.
D2 / W lamp
Photodiode array
LAAQ-B-LC001B
132
Data Obtained with a Photodiode
Array Detector
Spectrum
Absorbance
Chromatogram
LAAQ-B-LC001B
Retention time
133
Advantages of Photodiode Array
Detectors

Peak Identification Using Spectra
 Complementation
of identification based on
retention time
 Library searches

Evaluation of Peak Purity
 Purity
evaluation performed by comparison
of the shape of spectra from the peak
detection start point to the peak detection
end point
LAAQ-B-LC001B
134
Fluorescence Detector
Excitation wavelength
*
+ hv1
*
hv2 +
Excited state
Fluorescence wavelength
Quasi-excited state
hv1
hv2
LAAQ-B-LC001B
Fluorescence
Ground state
135
Optical System of Fluorescence Detector
Xenon lamp
Fluorescence
grating
Photomultiplier tube
Fluorescence
Excitation grating
LAAQ-B-LC001B
Excitation
Sample cell
light
136
Fluorescence Derivatization Reagents

OPA Reagent (Reacts with Primary Amines)
S-R’
CHO
+ R-NH2
CHO
R’-SH
N-R
o-phthalaldhyde
(OPA)

ADAM Reagent (Reacts with Fatty Acids)
+ R-COOH
CHN2
LAAQ-B-LC001B
CH2OCOR
9-anthryldiazomethane
(ADAM)
137
Differential Refractive Index
Detector (Deflection-Type)
Light-receiving unit
Reference cell
Light
Sample cell
LAAQ-B-LC001B
138
Optical System of Differential Refractive
Index Detector (Deflection-Type)
Slit
W lamp
Reference cell
Sample cell
The slit image moves if the
refractive index inside the
flow cell changes.
Photodiode
LAAQ-B-LC001B
139
Evaporative Light Scattering Detector
Light-receiving unit
Drift tube
Nebulizer
Column eluate
Nebulizer gas
Drain
Assist gas
Light source
The column eluate is evaporated and the light scattered
by the particles of nonvolatile substances is detected.
LAAQ-B-LC001B
140
Electrical Conductivity Detector
Pure water
NaCl aqueous
solution
Cl-
The bulb does not light with water.
LAAQ-B-LC001B
Na+
The bulb lights if there are ions.
141
Principle of Electrical Conductivity Detector
V
I
A
A
L
LAAQ-B-LC001B
I A
K   k
E L
L
k  K
A
Electrode
K:
I:
E:
A:
L:
k:
Electrical conductivity [S]
Electric current [A]
Voltage [V]
Electrode surface area [cm2]
Distance between electrodes [cm]
Specific electrical conductivity [S•cm-1]
142
Limiting Equivalent Ion Conductance, l
[S•cm2/mol], in Aqueous Solution (25ºC)
Cation
H+
Li+
Na+
K+
NH4+
(CH3)3NH+
Mg2+
Ca2+
LAAQ-B-LC001B
l
349.8
38.6
50.1
73.5
73.5
47.2
53.0
59.5
Anion
OH–
F–
Cl–
Br–
NO3–
CH3COO–
C6H5COO–
SO42–
l
198.3
55.4
76.3
78.1
71.4
40.9
32.3
80.0
143
Electrochemical Detector
Electrode
HO
R
HO
2e-
O
R
+ 2H+
O
LAAQ-B-LC001B
144
Cell Structure of Electrochemical
Detector (Amperometric Type)
Reference electrode
(Ag/AgCl)
Working electrode
(glassy carbon)
Eluent
Electrode couple
LAAQ-B-LC001B
145
Mass Spectrometer (LCMS)
Atmospheric
pressure
API probe
High vacuum
Quadrupole MS analyzer
Electron
multiplier tube
RP TMP1 TMP2
(high vacuum pumps)
LAAQ-B-LC001B
146
Atmospheric Pressure Ionization
Electrospray Ionization (ESI)
d
ge
ar
Ch
1)
Liquid Samples
Sample
Liquid
Neburaizing
Nebulizing Gas
Gas
High
High Voltage
Voltage
+
+
+
+- -+++
+
+-+-++
+
+
+
D
n
io
us
cl n
E x tio
on ra
ul po
Co va
3) n E
Io
n
io
at
ol nt
ap ve
Ev o l
2) of S
+
++- - + -+ +- + - +
+
et
pl
ro
Atmospheric Pressure Chemical Ionization (APCI)
Molecular ion reaction
Liquid Sample
Liquid
Samples
Nebulizing Gas
Neburaizing
Gas
LAAQ-B-LC001B
Heater
Heater
Corona
Colona Discharge
Discharge
Needle
Nnndle
147
Advantages of LCMS (1)

Quantitative analysis with excellent selectivity
m/z=100
A
TIC A:100
B
B:100
C:150 D:150
m/z=150
C
LAAQ-B-LC001B
D
148
Advantages of LCMS (2)

Peaks can be identified with MS spectra.
M/Z
M/Z
LAAQ-B-LC001B
M/Z
149
Comparison of Detectors
Absorbance
Fluorescence
Differential
refractive index
Evaporative light
scattering
Electrical
conductivity
Electrochemical
LAAQ-B-LC001B
Selectivity
Sensitivity
Possibility of
Gradient System
Light-absorbing
substances
ng
Possible
Fluorescent substances
pg
Possible
None
µg
Impossible
Nonvolatile substances
µg
Possible
Ionic substances
ng
Partially possible
Oxidizing / reducing
substances
pg
Partially possible
Note: The above table indicates general characteristics. There are exceptions.
150
Post-Column Derivatization
Reaction
chamber
Pump
Reaction
solution
LAAQ-B-LC001B
151
Application Examples of PostColumn Methods

Amino Acids




Arginine (fluorescence)
Bromate Ions

Orthophthalic acid, OPA
(fluorescence)
Ninhydrin (visible absorption)
Reducing Sugars




Cyanide Ions

Carbamate Pesticides

LAAQ-B-LC001B
Alkaline hydrolysis - OPA
(fluorescence)

Tribromide ionization
(ultraviolet absorption)
o-Dianisidine
(visible absorption)
Chlorination - pyrazolone
(visible absorption)
Transition Metal Ions

4-(2-Pyridylazo)
resorcinol, PAR (visible
absorption)
152
Quantitative Analysis
Absolute Calibration Curve Method
and Internal Standard Method
LAAQ-B-LC001B
153
Qualitative Analysis
Identification based on retention time
 Acquisition of spectra with detector

 UV
spectra
 MS spectra

Transfer to other analytical instruments
after preparative separation
LAAQ-B-LC001B
154
Quantitative Analysis
Quantitation performed with peak area or
height.
 Calibration curve created beforehand
using a standard.

 Absolute
calibration curve method
 Internal standard method
 Standard addition method
LAAQ-B-LC001B
155
Calibration Curve for Absolute
Calibration Curve Method
Concentration
Area
A1
Calibration curve
C1
A2
C2
Peak area
A4
A3
A2
A3
C3
A1
A4
C4
LAAQ-B-LC001B
C1
C2
C3
Concentration
C4
156
Concentration
Target Internal
substance standard
C1
Area
A1 AIS
CIS
A2 AIS
C2
CIS
A3 AIS
C3
CIS
A4 AIS
C4
CIS
LAAQ-B-LC001B
Area for target substance / Area for internal standard
Calibration Curve for Internal
Standard Method
Calibration curve
A4 /AIS
A3 /AIS
A2 /AIS
A1/AIS
C1/CIS C2 /CIS C3 /CIS C4 /CIS
Concentration of target substance /
Concentration of internal standard
157
Advantages of Internal Standard
Method (1)

Not affected by inconsistencies in injection volume.
X
IS
AX / AIS
10 µL
injected
Same area
ratio
IS
X
9 µL
injected
CX / CIS
LAAQ-B-LC001B
158
Advantages of Internal Standard
Method (2)
Not affected by the pretreatment recovery rate.
X
IS
AX / AIS

100%
recovery
rate
Same area
ratio
IS
90%
recovery
rate
X
CX / CIS
LAAQ-B-LC001B
159
Selection Criteria for Internal Standard





It must have similar chemical properties to the
target substance.
Its peak must appear relatively near that of the
target substance.
It must not already be contained in the actual
samples.
Its peak must be completely separated from those
of other sample components.
It must be chemically stable.
LAAQ-B-LC001B
160
Sample Pretreatment
Tasks Performed Before Injection
LAAQ-B-LC001B
161
Objectives of Pretreatment





To improve the accuracy of quantitative
values
To improve sensitivity and selectivity
To protect and prevent the deterioration of
columns and analytical instruments
To simplify measurement operations and
procedures
To stabilize target substances
LAAQ-B-LC001B
162
Substances That Must Not Be
Injected into the Column




Insoluble substances (e.g., microscopic
particles and precipitation)
Substances that are precipitated in the
eluent
Substances that irreversibly adsorb to the
packing material
Substances that dissolve, or chemically
react, with the packing material
LAAQ-B-LC001B
163
Filtration and Centrifugal Separation



In general, filter every
sample before injection!
It is convenient to use a
disposable filter with a
pore diameter of approx.
0.45 µm.
Centrifugal separation is
applicable for samples
that are difficult to filter.
LAAQ-B-LC001B
Filter
Syringe
164
Deproteinization

Precipitation
 Addition
of organic solvent (e.g., acetonitrile)
 Addition of acid (e.g., trichloroacetic acid,
perchloric acid)
 Addition of heavy metal or neutral salt

Ultrafiltration
LAAQ-B-LC001B
165
Solid Phase Extraction
(1)
(2)
Conditioning
Sample addition
(3)
Rinsing
(4)
Elution
Solvent with
low elution
strength
Solvent with
high elution
strength
Target
component
Unwanted
components
LAAQ-B-LC001B
166
Pre-Column Derivatization

OPA Reagent (Reacts with Primary Amines)
S-R’
CHO
+ R-NH2
CHO
N-R
R’-SH
o-phthalaldhyde
(OPA)

2,4-DNPH (Reacts with Aldehydes and Ketones)
NHNH2
+
O2 N
NO2
R
R’
NHN=C
C=O
H+
O2 N
R
R’
NO2
2,4-dinitrophenylhydrazine
(2,4-DNPH)
LAAQ-B-LC001B
167
Evaluation of the Reliability of
Analysis
Validation of Analytical Methods
LAAQ-B-LC001B
168
What Is “Validation of Analytical
Methods”?


Scientifically
demonstrating that the
analytical methods
concur with the
intended purpose (i.e.,
that errors are within a
permissible range)
Evaluating required
items from the
validation
characteristics
LAAQ-B-LC001B

Validation
characteristics








Accuracy / trueness
Precision
Specificity
Detection limit
Quantitation limit
Linearity
Range
(Robustness)
169
Accuracy / Trueness

Definition



Degree of bias in
measurements obtained with
analytical procedures
Difference between true value
and grand mean of
measurements
Evaluation Method


True value

Comparison with
theoretical values (or
authenticated values)
Comparison with results
obtained using other
analytical procedures for
which the accuracy
(trueness) is known
Recovery test
Measurement
Average
LAAQ-B-LC001B
95% confidence interval
170
Precision

Definition


LAAQ-B-LC001B

Repeatability / IntraAssay Precision
Degree of coincidence of
 Precision of
series of measurements
measurements taken over
obtained by repeatedly
a short time period under
analyzing multiple
the same conditions
samples taken from a
 Intermediate Precision
homogenous test
substance
 Reproducibility
Variance, standard
deviation, or relative
standard deviation of
measurements
171
Specificity

Definition



LAAQ-B-LC001B
The ability to accurately
analyze the target substance
in the presence of other
expected substances
The discrimination capability
of the analytical methods
Multiple analytical
procedures may be
combined in order to attain
the required level of
discrimination

Evaluation Method


Confirmation that the target
substance can be
discriminated (separated)
from co-existing
components, related
substances, decomposition
products, etc.
If reference standards for
impurities cannot be
obtained, the measurement
results for samples thought
to contain the impurities are
compared.
172
Detection Limit

Definition


The minimum quantity of
a target substance that
can be detected.
Quantitation is not
absolutely necessary.

Evaluation Method

Calculated from the
standard deviation of
measurements and the
slope of the calibration
curve.


Calculated from the
signal-to-noise ratio.

LAAQ-B-LC001B
DL = 3.3 s/slope
(s: Standard deviation of
measurements)
(Slope: Slope of calibration
curve)
Concentration for which
S/N = 3 or 2
173
Quantitation Limit

Definition


LAAQ-B-LC001B
The minimum quantity of a
target substance that can
be quantified
Quantitation with an
appropriate level of
accuracy and precision
must be possible. (In
general, the relative
standard deviation must
not exceed 10%.)

Evaluation Method

Calculated from the standard
deviation of measurements
and the slope of the
calibration curve.


QL = 10 s/slope
(s: Standard deviation of
measurements)
(Slope: Slope of calibration
curve)
Calculated from the signal-tonoise ratio.

Concentration for which S/N
= 10
174
Linearity

Definition


LAAQ-B-LC001B
The ability of the analytical
method to produce
measurements for the
quantity of a target
substance that satisfy a
linear relationship.
Values produced by
converting quantities or
measurements of the
target substance using a
precisely defined formula
may be used.

Evaluation Method


Samples containing
different quantities of the
target substance (usually
5 concentrations) are
analyzed repeatedly, and
regression equations and
correlation coefficients are
obtained.
Residuals obtained from
the regression equations
of the measurements are
plotted, and it is confirmed
that there is no specific
slope.
175
Range

Definition

LAAQ-B-LC001B
The region between
the lower and upper
limits of the quantity of
a target substance that
gives appropriate
levels of accuracy and
precision

Evaluation Method

The accuracy,
precision, and linearity
are investigated for
samples containing
quantities of a target
substance that
correspond to the
lower limit, upper limit,
and approximate
center of the range.
176
Robustness

Definition

LAAQ-B-LC001B
The ability of an
analytical procedure
to remain unaffected
by small changes in
analytical conditions.

Evaluation Method

Some or all of the
variable factors (i.e.,
the analytical
conditions) are
changed and the
effects are evaluated.
177
Maintenance of Separation Column
Extending the Column’s Service Life
LAAQ-B-LC001B
178
Silica-Based Packing Materials and
Resin-Based Packing Materials
Silica-Based
Resin-Based
pH range
2 - 7.5
Generally a wide
range
Organic
solvent
No restrictions
Significant
restrictions
Pressure
resistance
25 MPa max.
Low pressure
resistance
Temperature
60ºC max.
Depends on
packing material
LAAQ-B-LC001B
179
General Handling of Columns



Observe restrictions
related to solvents and
the pH range.
Never allow the
packing material to
dry.
Do not allow solids or
microscopic particles
to enter the column.

LAAQ-B-LC001B
Filter samples.

Use as low a load
pressure as possible.



Do not exceed the upper
pressure limit.
Do not subject the column
to sudden pressure
changes.
Do not subject the
column to intense
shocks.
180
Typical Problems (1)
Column Clogging

Preventive Measures



Filter samples.
Check that samples
dissolve in the eluent.
Get in the habit of
observing pressure
values.

Corrective Action




LAAQ-B-LC001B
Check for clogging in
parts other than the
column.
Rinse with an appropriate
solvent.
Connect the column in
reverse and flush out the
insoluble substances at a
low flow rate.
Open the column end
and perform ultrasonic
cleaning of the filter.
181
Typical Problems (2)
Peak Deformation
Cause
Corrective Action
Sample overload
Reduce the sample injection volume or
concentration.
Inappropriate sample
solvent
Replace the sample solvent with one of a
low elution capacity.
Dirt
Rinse the column.
Gap in column inlet
Repair the column by supplementing it
with packing material.
Influence of secondary
retention effects
Rinse the column.
Replace the column with one that is only
minimally influenced.
LAAQ-B-LC001B
182
Typical Problems (3)
Decrease in Retention Time

Check whether the
cause of the problem
is not the column.
Eluent composition
 Eluent flow rate
 Column temperature

LAAQ-B-LC001B

If the column is
identified as the
cause...
Rinsing
 Replacement

183
Typical Problems (4)
Baseline Drift

Check whether the
cause of the problem
is not the column.

LAAQ-B-LC001B
If the problem persists
when the column is
removed, it is caused
by the eluent, the
solvent delivery system
(pump or degasser), or
the detector.

If the column is
identified as the
cause...
Rinsing
 Review of
temperature control
 Replacement

184
Guard Column and Pre-column
Guard column
Pre-column
LAAQ-B-LC001B
185
Column Rinsing

Use an eluent with a high elution capacity



Reversed phase mode: Solution with a high proportion of
organic solvent
Ion exchange mode: Solution with a high salt
concentration
Consider secondary retention effects


LAAQ-B-LC001B
To remove basic substances from a reversed phase
column  Use an acidic solution and add an ion pair
reagent.
To remove hydrophobic substances from an ion
exchange column  Add an organic solvent.
186
Checking Column Performance
tR
N  16
W
H
W1/2
W
LAAQ-B-LC001B
H1/2
2
tR
 5.54
W1/ 2
 2
tR  H
Area
2
2
187
Column Storage

Storage Solution


It is generally safe to use
the same storage solution
as used at shipment.
In order to prevent
putrefaction, alcohol or
some other preservative
substance may be added.

Storage Conditions



LAAQ-B-LC001B
Insert an airtight stopper in
the column end. Never allow
the packing material to dry.
Make a record of the storage
solution and final usage
conditions and store it
together with the column.
Store the column in a
location not subject to shocks
or sudden temperature
changes.
188