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❃HPLC – High Performance Liquid Chromatography


HPLC – High Performance Liquid Chromatography


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1. Introduction

High Performance Liquid Chromatography (HPLC) is an advanced analytical technique used for the separation, identification, and quantification of components present in a mixture. It is based on the differential distribution of analytes between a stationary phase and a liquid mobile phase under high pressure.
HPLC is widely used in biochemistry, biotechnology, pharmaceuticals, food analysis, environmental studies, and clinical diagnostics.


2. Principle of HPLC

The principle of HPLC is based on partition, adsorption, ion-exchange, or size-exclusion mechanisms, depending on the type of column used.
A liquid mobile phase is pumped at high pressure through a column packed with fine stationary phase particles
Sample components interact differently with the stationary phase
Components with stronger interaction elute slower
Components with weaker interaction elute faster
Separated components are detected and recorded as chromatographic peak

OR

The principle of HPLC is based on the differential distribution of sample components between:
Stationary phase (solid or liquid supported on solid)
Mobile phase (liquid solvent)
Components interact differently with the stationary phase, leading to different retention times. Stronger interaction causes slower elution, while weaker interaction leads to faster elution. Separation occurs due to adsorption, partition, ion exchange, or size exclusion mechanisms.


3. Instrumentation of HPLC

HPLC system consists of the following major components:

3.1 Solvent Reservoir

Contains mobile phase solvents (water, methanol, acetonitrile, buffers)
Solvents must be HPLC grade
Degassing is necessary to remove air bubbles

3.2 pump

Delivers mobile phase at high pressure (up to 6000 psi)
Provides constant and reproducible flow rate
Types:
Reciprocating pump
Syringe pump
Pneumatic pump

3.3 Injector

Introduces sample into the mobile phase
Types:
Manual injector (Rheodyne valve)
Auto-sampler
Sample volume: 5–50 µL

3.4 Column

Heart of HPLC system
Packed with stationary phase particles (3–10 µm)
Common materials: silica, polymer-based particles
Column types:
Analytical column
Guard column


3.5 Detector

Detects eluted components and converts them into electrical signals.

Common detectors:

UV–Visible detector
Photodiode Array (PDA)
Fluorescence detector
Refractive Index (RI)
Electrochemical detector

3.6 Data System


Records chromatograms
Calculates retention time, peak area, and concentration

4. Types of HPLC


4.1 Normal Phase HPLC

Polar stationary phase (silica)
Non-polar mobile phase (hexane, chloroform)
Separation based on polarity


4.2 Reverse Phase HPLC (RP-HPLC)


Non-polar stationary phase (C18, C8)
Polar mobile phase (water + methanol/acetonitrile)
Most widely used method

4.3 Ion Exchange HPLC

Separation based on ionic interactions
Used for proteins, amino acids, nucleotides

4.4 Size Exclusion HPLC

Separation based on molecular size
Large molecules elute first
Used for polymers and proteins


5. Mobile Phase and Elution Methods

5.1 Isocratic Elution

Mobile phase composition remains constant
Suitable for simple mixtures.

5.2 Gradient Elution

Mobile phase composition changes during separation
Better resolution for complex mixtures

6. Important HPLC Parameters
Retention time (tR) – time taken for analyte to elute
Capacity factor (k') – retention strength
Resolution (Rs) – degree of separation between peaks
Theoretical plates (N) – column efficiency
Selectivity factor (α) – relative separation of components


7. Applications of HPLC

Pharmaceutical analysis (drug purity, stability testing)
Clinical analysis (blood, urine samples)
Food and beverage quality control
Environmental monitoring (pesticides, pollutants)
Plant tissue culture and secondary metabolite analysis
Biotechnology (protein and peptide separation)

8. Advantages of HPLC


High resolution and sensitivity
Fast and accurate analysis
Suitable for non-volatile and thermally unstable compounds
Quantitative and qualitative analysis possible
Automation and reproducibility

9. Limitations of HPLC


High cost of equipment and maintenance
Requires skilled personnel
Uses large volumes of organic solvents
Column degradation over time


10. Conclusion


HPLC is a powerful and versatile analytical technique that plays a crucial role in modern analytical laboratories. Its high precision, efficiency, and adaptability make it indispensable in pharmaceutical, biochemical, environmental, and plant science research. Continuous advancements in column technology and detectors have further enhanced its analytical performance.




50 MCQs ABOUT HPLC (WITH ANSWERS)

1. HPLC stands for
A. High Pressure Liquid Chromatography
B. High Performance Liquid Chromatography
C. High Precision Liquid Chromatography
D. High Polarity Liquid Chromatography
Answer: B
2. The principle of HPLC is based on
A. Differential volatility
B. Differential partitioning
C. Differential migration
D. Differential distribution between phases
Answer: D
3. The mobile phase in HPLC is
A. Gas
B. Solid
C. Liquid
D. Supercritical fluid
Answer: C
4. Which component delivers high pressure in HPLC?
A. Injector
B. Column
C. Pump
D. Detector
Answer: C
5. Typical operating pressure in HPLC is
A. 1–10 psi
B. 10–100 psi
C. 100–1000 psi
D. Up to 6000 psi
Answer: D
6. The most commonly used HPLC mode is
A. Normal phase
B. Reverse phase
C. Ion exchange
D. Size exclusion
Answer: B
7. In reverse phase HPLC, the stationary phase is
A. Polar
B. Non-polar
C. Ionic
D. Volatile
Answer: B
8. C18 column is also called
A. ODS column
B. Silica column
C. Alumina column
D. Polymer column
Answer: A
9. The particle size of HPLC column packing material is usually
A. 50–100 µm
B. 20–30 µm
C. 3–10 µm
D. 0.1–1 µm
Answer: C
10. Which detector is most commonly used in HPLC?
A. Flame ionization detector
B. UV–Visible detector
C. Thermal conductivity detector
D. Electron capture detector
Answer: B
11. Retention time is defined as
A. Time for sample injection
B. Time taken for analyte to reach detector
C. Time for solvent evaporation
D. Time for column washing
Answer: B
12. Gradient elution means
A. Constant mobile phase composition
B. Change in flow rate
C. Change in mobile phase composition
D. Change in column length
Answer: C
13. Isocratic elution means
A. Variable solvent composition
B. Constant solvent composition
C. Variable temperature
D. Variable pressure
Answer: B
14. Which solvent is commonly used in RP-HPLC?
A. Hexane
B. Chloroform
C. Methanol
D. Benzene
Answer: C
15. Degassing of mobile phase is required to
A. Increase pressure
B. Remove dissolved gases
C. Improve column life
D. Increase viscosity
Answer: B
16. Which parameter indicates column efficiency?
A. Resolution
B. Retention time
C. Theoretical plates
D. Selectivity
Answer: C
17. Resolution in HPLC refers to
A. Speed of analysis
B. Separation between two peaks
C. Peak height
D. Detector sensitivity
Answer: B
18. Guard column is used to
A. Detect analytes
B. Increase pressure
C. Protect analytical column
D. Increase resolution
Answer: C
19. Which HPLC type separates compounds based on charge?
A. Normal phase
B. Reverse phase
C. Ion exchange
D. Size exclusion
Answer: C
20. Size exclusion HPLC separates molecules based on
A. Polarity
B. Charge
C. Molecular size
D. Boiling point
Answer: C
21. In size exclusion chromatography, which elutes first?
A. Small molecules
B. Medium molecules
C. Large molecules
D. Polar molecules
Answer: C
22. Which detector is suitable for non-UV absorbing compounds?
A. UV detector
B. PDA detector
C. RI detector
D. Fluorescence detector
Answer: C
23. PDA detector provides information about
A. Pressure
B. Temperature
C. Full UV spectrum
D. Flow rate
Answer: C
24. Typical sample injection volume in HPLC is
A. 1–2 mL
B. 500 µL
C. 5–50 µL
D. 100 mL
Answer: C
25. Which material is commonly used as stationary phase support?
A. Cellulose
B. Silica
C. Agar
D. Charcoal
Answer: B
26. Which factor does NOT affect retention time?
A. Mobile phase composition
B. Flow rate
C. Column temperature
D. Detector wavelength
Answer: D
27. HPLC is especially useful for analyzing
A. Volatile compounds
B. Thermally stable compounds
C. Non-volatile compounds
D. Gaseous samples
Answer: C
28. Which pump provides pulse-free flow?
A. Reciprocating pump
B. Syringe pump
C. Pneumatic pump
D. Peristaltic pump
Answer: B
29. Capacity factor (k') indicates
A. Peak height
B. Retention strength
C. Detector response
D. Flow rate
Answer: B
30. Selectivity factor (α) is a measure of
A. Column length
B. Separation between two solutes
C. Mobile phase strength
D. Detector efficiency
Answer: B
31. Which HPLC component introduces the sample?
A. Pump
B. Injector
C. Detector
D. Column
Answer: B
32. Which solvent is non-polar?
A. Water
B. Methanol
C. Acetonitrile
D. Hexane
Answer: D
33. Normal phase HPLC uses
A. Non-polar stationary phase
B. Polar stationary phase
C. Aqueous mobile phase
D. Buffer only
Answer: B
34. HPLC is preferred over TLC because of
A. Lower cost
B. Better resolution and quantification
C. Simpler operation
D. No solvent use
Answer: B
35. Which detector is highly sensitive and selective?
A. RI detector
B. UV detector
C. Fluorescence detector
D. TCD
Answer: C
36. Column temperature control improves
A. Flow rate
B. Reproducibility
C. Detector sensitivity
D. Injection volume
Answer: B
37. Which HPLC mode is used for protein purification?
A. Normal phase
B. Ion exchange
C. Reverse phase
D. Adsorption
Answer: B
38. Which parameter is calculated from peak area?
A. Retention time
B. Concentration
C. Flow rate
D. Pressure
Answer: B
39. The heart of the HPLC system is
A. Pump
B. Injector
C. Column
D. Detector
Answer: C
40. Which solvent is least polar?
A. Water
B. Methanol
C. Acetonitrile
D. Hexane
Answer: D
41. HPLC data output is called
A. Spectrogram
B. Chromatogram
C. Electropherogram
D. Thermogram
Answer: B
42. Which technique is NOT a type of HPLC?
A. Ion exchange
B. Size exclusion
C. Gas chromatography
D. Reverse phase
Answer: C
43. Column efficiency increases when particle size is
A. Increased
B. Decreased
C. Unchanged
D. Doubled
Answer: B
44. Which factor increases back pressure?
A. Larger particle size
B. Lower flow rate
C. Smaller particle size
D. Shorter column
Answer: C
45. HPLC is widely used in pharmaceutical industry for
A. Drug synthesis
B. Drug formulation
C. Drug analysis and quality control
D. Drug packaging
Answer: C
46. Which detector cannot be used with gradient elution?
A. UV detector
B. PDA detector
C. RI detector
D. Fluorescence detector
Answer: C
47. Which parameter represents separation power of column?
A. Retention time
B. Resolution
C. Flow rate
D. Injection volume
Answer: B
48. Which compound elutes first in RP-HPLC?
A. Non-polar compound
B. Polar compound
C. High molecular weight compound
D. Aromatic compound
Answer: B
49. Which mobile phase component controls pH?
A. Organic solvent
B. Buffer
C. Detector
D. Column
Answer: B
50. HPLC is an example of
A. Planar chromatography
B. Column chromatography
C. Paper chromatography
D. Affinity chromatography
Answer: B


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