Different Types of HPLC Detectors

1. UV/Vis Absorbance Detector

• Principle: Measures absorbance of analytes at a specific wavelength (Beer-Lambert Law).

• Types:

  • Fixed Wavelength UV (e.g., 254 nm)

  • Variable Wavelength UV

  • Diode Array Detector (DAD/PDA) – allows spectral scanning.

• Applications: Compounds with UV chromophores (e.g., APIs, impurities).

• Advantages: High sensitivity, widely used, cost-effective.

2. Fluorescence Detector (FLD)

• Principle: Measures fluorescence emitted by analytes after excitation with UV light.

• Applications: Highly sensitive detection of compounds like vitamins, proteins, drugs with native fluorescence or after derivatization.

• Advantages: Selective and very sensitive (up to 100–1000× more sensitive than UV).

3. Refractive Index Detector (RID)

• Principle: Detects changes in refractive index of the mobile phase caused by analytes.

• Applications: Sugars, lipids, polymers, compounds without UV absorbance.

• Advantages: Universal detector, simple to operate.

• Limitations: Less sensitive, cannot be used with gradient elution.

4. Evaporative Light Scattering Detector (ELSD)

• Principle: Mobile phase is evaporated, and light scattering from analyte particles is measured.

• Applications: Non-volatile and semi-volatile analytes without chromophores (e.g., lipids, sugars).

• Advantages: Detects compounds that UV or RID cannot.

5. Conductivity Detector

• Principle: Measures ionic conductivity changes.

• Applications: Ion chromatography, inorganic ions, ionic drugs.

• Advantages: Highly selective for ionic species.

6. Mass Spectrometry Detector (LC–MS)

• Principle: Ionizes analytes and measures mass-to-charge ratio (m/z).

• Applications: Structure elucidation, trace-level quantification, pharmacokinetics, impurity profiling.

• Advantages: High sensitivity, specificity, and qualitative/quantitative capabilities.

7. Electrochemical Detector (ECD)

• Principle: Measures current produced by oxidation or reduction of analytes at an electrode surface.

• Applications: Neurotransmitters, vitamins, certain drugs.

• Advantages: Extremely sensitive for electroactive compounds.

8. Charged Aerosol Detector (CAD)

• Principle: Nebulized mobile phase, charged aerosol particles detected.

• Applications: Lipids, carbohydrates, peptides, polymers.

• Advantages: Universal detection, gradient-compatible.