3.3.8 Detectors
There are a variety of detectors available for use with HPLC. These range from near universal detectors that will respond to any organic chemical structure to specialty detectors that only respond to a few analytes. Both have their advantages. Universal detectors provide economic use for a large diversity of chemicals but specific analyte detection can be hampered if two or more analytes elute from the analytical column at the same retention time. Specialty detectors provide near-interference free detection of only a few analytes. Common detectors, along with their use and approximately detection limits are given in Table 3.1.
Table 3.1. Common Commercially Available HPLC detectors, Applications, and Detection Limits.
| Detector | Application(s) | Detection Limits |
|---|---|---|
| UV-Visible Absorbance | For compounds that absorb in the UV or visible range |
pg quantities |
| Fluorescence | For compounds capable of fluorescence (especially polyaromatic hydrocarbons) |
fg quantities |
| Refractive Index (RI) | For alcohol, sugar, saccharide, fatty acid, and polymer analysis with refractive indices different from the solvent | ng quantities |
| Electrochemical | For analyzing a wide range of compounds | high pg quantities |
| Conductivity for IC | Mainly for inorganic ions | ~ng quantities |
| Evaporative Light Scattering (ELS) | For a wide variety of compounds that lack UV/Vis chromophores including triglycerides, sugars and natural products | μg quantities |
| Fourier Transfer Infrared | For compounds with vibrational functional groups | μg quantities |
| Mass Spectrometry | A universal detector | μg to pg quantities depending on the type of mass spectrometer |
The most common detector is the UV-Vis detector that comes standard on basic HPLC systems. This is a near-universal detector since most organic compounds have a chromophore capable of adsorbing UV or visible wavelengths. The focus of this textbook, mass spectrometer detectors, will be discussed in the next chapter.
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