Date post: | 27-Dec-2015 |
Category: |
Documents |
Upload: | vincent-ramsey |
View: | 220 times |
Download: | 1 times |
HPLC Instrumentation and
Applications
Other names for HPLC1- High Speed Liquid Chromatography
- As the separation is completed within few minutes.2- High Performance Liquid Chromatography
(HPLC)3- High Resolution Liquid Chromatography (HRLC)High performance is the result of many factors:
- Smaller particles of the stationary phase, uniform pore size, high pressure column slurry packing technique, accurate low volume of the sample injected, sensitive detector, and good pump system
IntroductionHigh pressure liquid chromatography (HPLC) is
an advanced form of liquid chromatography used to separate the components of a mixture (Analytes).
In HPLC chromatography: the mixture is dissolved in a solvent (mobile phase) and then forced to flow through a chromatographic column under a high pressure. In the column, the mixture is resolved into its components.
The separation occurs because each component in the mixture interacts differently with the stationary phase. Molecules that interact strongly with the stationary phase (yellow component) will move slowly through the column, while the molecules that interact less strongly (blue component) will move rapidly through the column.
The start to the detector
-Why high pressure?- In HPLC the stationary phase has two characters :- - Has small particles size (5- 10 µm). - - And packed under high pressure.- Reduction of the particle size of the stationary phase
leads to: - Leaving less space for the mobile phase to pass
through. - Decrease the flow rate of the liquid mobile phase.- Thus pressure from 1000 to 5000 psi, pound per
square inch (68 to 340 atm.) is applied to overcome the obstructive effect of the fine particles.
Classification of HPLCI- Types of HPLC according to the mechanism of
separation1- Adsorption chromatographyThe stationary phase is an adsorbent and
the separation is based on adsorption-desorption steps.
A- Normal phase chromatographyThe stationary phase is strongly polar (e.g.
silica gel) and the mobile phase is non polar such as (hexane or tetrahydrofuran).
Polar sample retained longer on the column.
B- Reversed Phase chromatography
The stationary phase is strongly non polar ( e.g. C-18 silica , hydrpophobic) while the mobile phase is polar (as a mixture of water and methanol or acetonitrile).
2- Size exclusion chromatography.
The column is packed with material having controlled pore sizes and the sample is screened or filtered according to its molecular size, there is no interaction between solute and stationary phase. The large molecules rapidly washed through the column, the smaller molecules penetrate inside the pores and elute later.
Large molecules
Small molecules
3- Ion exchange chromatographyThe stationary phase has an ionically charged
surface of opposite charge to the sample ions
- This technique is used only for ionic or ionisable samples.
Types of St. Ph
1- Anion exchange resin2- Cation exchange resinMatrix: is polymer of styrene with
divinyl benzene
Anaion exchange as:- strong anion as quaternary ammonium
form Matrix- (NR3)+ -Cl-
- weak anion as Matrix-NH2(CH3)-Cl-
Cation exchange as: sulfonic acid Matrix-(SO3)– H+
(strong). And Matrix-COO- H+ (weak)The stronger the charge on the sample, the stronger it
will be attached to the ionic surface and thus the longer it will take to elute.
The mobile phase is an aqueous buffer, where the PH is adjusted to control elution time.
Choice of separation technique1- Sample molecular weight less than 2000
Water soluble Ionic
Non- ionic
Reversed phase Chrom. (RPC)Ion exchnge Chrom.(IEC)
Reversed phase Chrom. (RPC)Exclusion Chrm. (EC) if soluble in tetrahydrofuran
Organic solvent soluble non polar solvent----Adsorption chromatography
Tetrahydrofuran------ Exclusion Chrm. (EC)
Polar solvent------Normal phase chromatography ------Reversed phase chromatography
2- Sample molecular weight greater than 2000
Water soluble
Organic solvent soluble
Reversed phase chromatography (RPC)
Ion exchnge Chrom. (IEC)
Exclusion Chrm. (EC)
Exclusion Chrm. (EC)
II- HPLC can be divided into two main types according to the uses:
1- Analytical type: which is useda- In identification and assay of the
components in a mixture .b- To know the number of components
in a mixture (screening).2- Preparative or semipreparative
type: used in isolation and purification.
The difference between analytical and preparative HPLC
1- Dimensions of the column.- Analytical, 1-6 mm i. d. - Preparative up to 3 cm i. d.2- Flow rate of mobile phase (pump).For analytical HPLC pumps should
has flow rates that range from 1 to 10 ml/min.
but for preparative HPLC, flow rates in excess of 100 ml/min.
3- Injected volume of the sample- in analytical HPLC range from 20 uL
to 1 mL, - but in preparative or semi
preparative from 1 ml to 5 ml or more.
- 4- Size of the loop of injection port.
Chromatographic processThe process begins by:- Injecting the solute
onto the column (zero time).
- The separation occurs as the analyte and mobile phase are pumped through the column
- Detection of components by detector is displayed on a chart or computer screen (chromatogram).
The advantages of HPLC1- High speed2- High resolution3- High sensitivity4- Re-usable column5- No destruction of the components6- The instrumentation are automatic,
computerized7- Sample is recovered completely8- Quantitative work is more easily and most
sensitive
Instrumentation of HPLCHPLC instrument includes:A- Reservoir for solvents (mobile phase)B- High pressure pumpC- Sample inlet device D- ColumnE- DetectorF- Recorder
A- Reservoir for solvents (mobile phase)
-Mobile phase is usually organic or aqueous or mixture of both.
- Mobile phase is placed in bottles of glass.
Mobile phase
Miscible with water, such as acetonitrile, methanol, or isopropanol.
Characters of mobile phase:
1- Pure 2 - Low viscosity
3-Chemically inert 4- Low price
5- Compatible with detector
6- Solubility of the sample
Mobile phase
Solvent A Solvent B
Water Organic solvent
Elution Techniques (Programinig)1- Isocratic elution:The mobile phase composition remains constant
throughout the separation procedure.
2- Gradient elution:The mobile phase composition is changed during
the separation process.
Gradient elution is divided into two types:
A- Continuous (linear)
B- Discontinuous (stepwise)
Isocratic and gradient elution curves
Stepwise (discontinuous)
Linear (continuous)
Time
% of B
10%
20%
30%
40%
50%
60%
70%
0 5` 10` 15` 20` 25` 30`
Isocratic elution
Gradient elution
Advantages of gradient elution technique
1- Shortening the time of analysis.2- Reduces tailing, gives sharp peak.3- Increases the sensitivity of analysis.4- Decreases the retention of the later-eluting components so that they elute faster.
PH of mobile phaseThe pH of the solvent (water) may be adjusted
using phosphate or perchlorate or trifloroacetate acid or sulphate buffer.
The selectivity of HPLC is affected by :1- Type of mobile phase, organic or aqueous.
2- The composition of the mobile phase, whether one solvent or more.
3- The pH of the mobile phase.
Effect of buffer used in separationof xanthene alkaloids
TFAIncomplete
separation
HClO4No separation for 2
and 3
H2SO4Best separation
30% MeCN
70% Water
45% MeOH
55% Water
Mobile Phase Composition Effect on Selectivity
Fast Slow and better separation
Methanol and water give slow and better separation while use of actonitrile and water give fast and bad separation
% of Mobile phase B (MeOH) and separation selectivity
High % of B givesfast and bad separation
Low % of B givesslow and slightly better separation
Some solvents used in HPLC and their polarity
N.B. Chlorinated solvents do not used in HPLC to prevent rusting of stainless parts of the instruments
Solvents PolarityWater
Dimethyl sulfoxideEthylene glycol
AcetonitrileMethanolAcetoneDioxaneEthanol
TetrahydrofuranI-propanol
10.27.26.95.85.15.14.84.34.03.9
Treatment of mobile phaseA- Filtration before entering the column.B- Degassing using degasser.- 1- Heating with stirring - 2- Applying vacuum, - 3- Passing nitrogen or helium- 4- UltrasoundC- Pre-saturation with the stationary phase in
case of liquid liquid chromatography.
B- PumpFunction of the pump:Pump is used for forcing the mobile phase through the columnThere are two types of pump:1- Constant pressure pumpIt is free from pulsation resulting in smooth baseline2- Constant flow pump It is able to give constant flow rate of
mobile phase
To column
Mobile phase
The main criteria for the pump
1- The pump should be capable of
delivering accurate and pulse free flow rate (e.g. 5 ml/min).
2- The pump should be capable of delivering high volume of solvent.
3- The pump should be capable of delivering high pressure up to 5000 psi.
C- Sample inlet device(Injection port)
1- Manual injection 2-Automated injection
The injection port consists of A- The injection valve. B- The sample loop.
Manual injection
1- The sample is typically dissolved in the mobile phase. 2- It is drawn into a syringe and injected into the loop via injection valve.
D- ColumnColumn in HPLC is either
Different shapes for columns used in HPLC
1- Analytical, 1-6 mm i. d.
2- Preparative up to 3 cm i. d.
Made from: Stainless
Shape: StraightLength: Variable
Other types of columns used in HPLC
Guard column:1- Protect the
analytical column2- Organization
of separation in HPLC
E- Detectors (Brain of HPLC)Characters of detector
1- High sensitivity
2- Low noise (straight base line)
3-Wide range of response to different compounds
4- Unaffected by temperature or mobile phase
5- Non destructive to the compounds
6- Provides qualitative and quantitative information about the detected sample
Types of Detectors1 -UV absorption detector - It is the most sensitive, sensitive
to ng of compound.- The most widely used, it measure
the UV absorption of the solute.
2 - Refractive index detector
-Not used in case of gradient elution -- Less sensitive-It measures the difference in RI between pure mobile phase and the column eluate (mobile phase + solute).
3- Mass spectrometer detector It is used with capillary column in analytical
HPLC to give information about nature of the material by giving the mass spectrum of the material.
4- Fluorescence detector- More sensitive than UV detector (1000 fold as UV)
- It is used with compounds which are naturally fluorescent. Or compound which
- can be converted to fluorescent- derivative.
5- Photodiode array detector- It is series of detectors each is responsible
for receiving a different wavelength.
6-Flame ionization detector- Used for substances whose boiling point is
higher than that of the mobile phase- - It is more sensitive than refractive index
detector
Applications of HPLC1- Isolation and purification of
biologically active natural products2- Control of synthetic reactions Identification of intermediates and
target compound.3- Biosynthesis study Detection of biogenetic
intermediates and enzymes involved.4-Control the microbiological processUsed for separation of antibiotic from
broth mixture
5- Pharmacokinetics study Pharmacokinetic study comprises the
measurement of drug metabolites concentration in body fluids, absorption, bioavailability and elimination of drugs
HPLC determines the drug and its metabolites in one step.
6- Stability test Rapid method of analysis in stability test.7- Quality control HPLC is used to know the identity, purity
and content of the ingredients (drugs, raw and pharmaceutical products,
8- Drugs metabolisms
Applications of HPLC in isolation and purification of natural products
I. Purification refers to the process of separation or extraction the target compound from other compounds or contaminants.
1- Separation of quinine and quinidine
N
H
HO
N
MeO
H
H
5`6`
7`
8` 1`
2`3`
4`
891
2
3
4
5
6
7
R
S
N
HO
H
N
R
H
5`6`
7`
8` 1`
2`3`
4`
91
2
3
4
5
6
7
H
8
R
S
1- Quinidine2- Qinine
12
2- Separation of Xanthines alkaloids
N
NH
N
N
O
1
23 4
98
756
O
2- 1,7 Dimethylxanthine
N
NN
HN
O
1
23 4
98
756
O
3- Theophylline1,3 Dimethylxanthine
HN
NN
N
O
1
23 4
98
756
O
1- Theobromine3,7 Dimethylxanthine
3- Separation of vitamin B-1, 2, 6Column: Primesep 150x4.6
mmFlow rate: 1ml/minDetection: UV 280
nmMobile phase:
MeCN/H2O (10/90)With H3BO4 bufferPH 3.0
4- Separation of ascorbic acid and dehydro-ascorbic acid
Column: Primesep50x4.6 mmFlow rate: 1ml/minDetection: UVMobile phase:
MeCN/H2O (10/90)With HCOOH buffer0.1%.
5- Separation of chloramphenicol from mixture of antibiotics
6- Separation of mixture of alkaloids1- Codeine2- Strychnine3- Papaverine4- Quinine5- Quinidine
II- Quantitative (assay) and qualitative determination of natural products
Quantification of compounds by HPLC Is the process of determination of the unknown
concentration of a compound in a known solution.
Identification of compound by HPLC through :- Comparison of retention time with authentic- Comparison of UV spectrum of the compound
with that of the authentic.- Comparison of the Mass spectrum with that of
the authentic.-
Quantification of oroidin in Axinella damicornis sponge (assay)
Oroidin is known alkaloid isolated from sponge Axinella damicornis and it was identified by HPLC through the comparison of retention time and UV absorption with data base on HPLC.
NH
Br
Br
O
HN
NH
HN NH2
1
2
34
56
7
8
9
10
11
1213
1415
+
Steps of assay1- Quantification was done by injection of
different known conc. of oroidin (authentic).2- determination of the peak area for each
concentration3- Followed by drawing the standard curve
(area under the peak against conc.).4- Injection of known weight of the sponge
extract and find the area under the peak.5- From the standard curve find the
corresponding concentration of oroidin in the injected weight.
6- Calculate the weight of oroidin in the sponge.
Standard curve of oroidin
160 mg was found to be the conc. of oroidin in one gram of the sponge