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HPLC Detector

Overview

The instrument component in the HPLC system that senses the separated compounds eluting from the column, and provides the electronic signal to the Computer Data Station or Recorder to create the chromatogram. Because sample compounds have differing charateristics, several different types of detectors are available. For example, if a compound can absorb ultaviolet light, then a UV Absorbance Detector is used. If the compound can fluoresce, then a Fluoresence Detector is used. If the compound does not have either of these characteristics then a more universal type of detector is used such as Evapoarative Light Scattering Detector (ELSD).

Today, the most powerful approach to gain as much information as possible from a run, is to use multiple detectors in series. Typically, a UV and ELSD detector are used in combination with a Mass Spectrometer (MS) to analyze the results of the chromatographic separation.

Types of Detectors

  • UV - Ultraviolet
    • Lamp
    • Grating/Lens - Wave length
    • FlowCell
    • PhotoDiode - Differential Light Output
  • RI - Refractive Index
    • Universal analyte detector
    • Solvent must remain the same throughout the separation
    • VERY temperature sensitive
    • Somewhat difficult to stabilize baseline
  • FD - Fluorescence
    • Excitation wavelength generates fluorescence emission at higher wavelength
    • Analytes must have fluoropore group
      • Can react analyte with fluoropore reagent
    • Very sensitive and selective
    • More difficult methods transfer
    • Results vary dependent upon separation conditions
  • MS - Mass Spec
    • Mass to charge ratio (m/z)
    • Allows specific compound ID
    • Several types of ionization techniques
      • electrospray, atmospheric pressure chemical ionization, electron impact
  • ELSD - Evaporative Light Scattering Detector
    • Used for analytes that have poor to no UV/Vis response or do not ionize well under mass spectrometry
      • Nebulizer for aerosol formation
      • Drift tube for the desolvation process
      • Scatter chamber for detecting particles formed
      • Lamp