Plate Theory
Definition
Model that treats a column as a series of theoretical plates. The Height Equivalent to a Theoretical Plate (HETP) measures column efficiency; lower HETP means better separation.
Related terms
- ECD
- Electron capture detector. A Ni-63 radioactive source produces a baseline electron current that is reduced when electron-affinic species (halogens, nitro groups, peroxides)...
- FID
- Flame ionisation detector. A hydrogen-air flame ionises C-H bond containing analytes and a collector electrode reads the ion current. Near-universal for organic...
- Isocratic vs Gradient Elution
- Isocratic means the mobile-phase composition stays constant through the run; simple, reproducible, but limited resolving power for wide-polarity mixtures. Gradient means the...
- Mobile Phase
- The solvent or mixture that flows over the stationary phase and carries analytes along. Polarity, viscosity and volatility set the separation; switching...
- MSD
- Mass Selective Detector. GC-MS or LC-MS detector that identifies analytes by mass spectrum. The confirmation standard for drug and toxicology casework.
- Partition vs Adsorption
- Partition chromatography separates by differential solubility between two liquid phases (GLC, reversed-phase HPLC). Adsorption chromatography separates by surface binding to a solid...
- Rf Value
- The retention factor, defined as the distance the spot travels divided by the distance the solvent front travels on the same plate....
- Stationary Phase
- The immobile material the mixture flows past. In paper it is water inside cellulose fibres; in classical column work and TLC it...
Explained in
- Chromatographic Techniques in Forensic Science: TLC, GLC, HPLC and HPTLCModel that treats a column as a series of theoretical plates. The Height Equivalent to a Theoretical Plate (HETP) measures column efficiency; lower HETP means...