Introduction & Theory of HPLC

Introduction & Theory of HPLC

Introduction and Theory of HPLC explains separation of compounds using high pressure liquid mobile phase and stationary phase.

Introduction to HPLC

• Definition: An advanced liquid chromatography method for separating, identifying, and quantifying mixture components.
• Pharmaceutical Use: Widely adopted for its accuracy and reliability.
• Advancement: Unlike traditional liquid chromatography that uses gravity, HPLC employs high pressures to enhance separation and analysis precision.

Theory of HPLC

HPLC operates on the principle of partitioning analytes between a mobile phase and a stationary phase.

Key Concepts

1. Mobile Phase

   • Role: Solvent(s) that transport analytes through the column under high pressure.

2. Stationary Phase

   • Role: Packed column with coated particles that interact differently with each analyte, causing varied retention times.

3. Partitioning

   • Mechanism: Analytes distribute between mobile and stationary phases based on their affinities.

4. Separation

   • Outcome: Different retention times lead to the separation of compounds.

5. Detection

   • Process: Eluted compounds pass through a detector, generating a chromatogram (signal vs. time/volume).

Types of Interactions in HPLC

1. Normal Phase HPLC (NP-HPLC)

   • Stationary Phase: Polar (e.g., silica)
   • Mobile Phase: Less polar (e.g., hexane)
   • Separation Basis: Polarity

2. Reverse Phase HPLC (RP-HPLC)

   • Stationary Phase: Non-polar or weakly polar
   • Mobile Phase: Polar
   • Usage: Most common in pharmaceuticals

3. Ion-Exchange HPLC

   • Stationary Phase: Charged groups
   • Separation Basis: Charge properties

4. Size Exclusion HPLC (SEC/GPC)

   • Separation Basis: Molecular size
   • Mechanism: Larger molecules elute first by exclusion from pores

Modes of Mobile Phase Delivery

1. Isocratic Elution

   • Definition: Constant mobile phase composition throughout the run.
   • Advantages: Simple setup, high reproducibility.
   • Limitations: Less effective for complex mixtures, potential peak broadening.

2. Gradient Elution

   • Definition: Mobile phase composition changes during the run.
   • Advantages: Better separation for diverse compounds, sharper peaks, faster analyses.
   • Limitations: More complex equipment, requires precise control for reproducibility.

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