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HPLC Detectors – Types and Their Applications in Pharma

HPLC Detectors – Types and Their Applications in Pharma 🔍

After a sample is separated by the HPLC column, it needs to be detected and measured. This is where HPLC detectors come in. Detectors help us know what compound is coming out of the column and how much of it is present. Different detectors are used depending on the chemical nature of the compound.

1. UV-Visible Detector (UV/Vis & DAD) 🌈

This is the most commonly used detector in pharmaceutical analysis. It measures how much UV or visible light a compound absorbs.

  • Single Wavelength UV: Measures absorbance at one fixed wavelength (e.g., 254 nm).
  • DAD – Diode Array Detector: Records absorbance across a range of wavelengths. It helps in identifying peak purity and overlapping compounds.
  • Best for: UV-absorbing compounds like drugs with aromatic rings or conjugated systems.
  • Example: Paracetamol, aspirin, ibuprofen, antihistamines

2. Fluorescence Detector ✨

This detector measures the light emitted (fluorescence) by certain compounds when excited by UV or visible light. It is highly sensitive and ideal for trace analysis.

  • Best for: Naturally fluorescent compounds or derivatized analytes
  • Example: Vitamins (like B2), hormones, some antibiotics
  • Sensitivity: Much higher than UV detectors

3. Refractive Index Detector (RI) 💧

This universal detector measures the change in refractive index of the mobile phase as the compound passes through.

  • Best for: Compounds that don’t absorb UV (e.g., sugars, alcohols)
  • Limitation: Not suitable for gradient methods; less sensitive than UV

4. Mass Spectrometry Detector (LC-MS) ⚖️

This advanced detector identifies compounds based on their mass-to-charge (m/z) ratio. It provides both qualitative and quantitative data.

  • Best for: Trace-level detection and molecular structure confirmation
  • Example: Metabolites, drug impurities, bioavailability studies
  • Sensitivity: Extremely high and specific

5. Conductivity Detector ⚡

Measures the electrical conductivity of the eluent. It is mostly used for ionic compounds and inorganic analysis.

  • Best for: Ions, salts, water analysis
  • Example: Electrolytes in injections, raw material testing

Comparison Table 📊

Detector Detection Principle Best For Sensitivity
UV/Vis Absorbance of UV/visible light Most pharma drugs Moderate to High
DAD Multi-wavelength absorbance Peak purity, overlapping peaks High
Fluorescence Fluorescence emission Trace analysis Very High
RI Refractive index change Sugars, non-UV compounds Low
Mass Spec (LC-MS) Mass-to-charge ratio Structural analysis Extremely High
Conductivity Electrical conductivity Ions, salts Medium

Summary ✅

  • UV/DAD: Common in most pharma labs
  • Fluorescence: Used for highly sensitive trace analysis
  • RI: Ideal for sugars and alcohols
  • LC-MS: For complex identification and precision
  • Conductivity: For electrolytes and water-soluble ions

Keywords 🔑

HPLC detectors, DAD in HPLC, UV detector in pharma, LC-MS chromatography, fluorescence detector HPLC, RI detector, types of HPLC detectors, pharma testing methods

Written by Nirmal Patel | o2h.space

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