Chromatography terms / analyte / Analytical chromatography / bonded phase / chromatogram /...

  • The analyte is the substance to be separated during chromatography. It is also normally what is needed from the mixture.
  • Analytical chromatography is used to determine the existence and possibly also the concentration of analyte(s) in asample.
  • A bonded phase is a stationary phase that is covalently bonded to the support particles or to the inside wall of the column tubing.
  • A chromatogram is the visual output of the chromatograph. In the case of an optimal separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture.
Chromatogram with unresolved peaks 
Chromatogram with two resolved peaks
Plotted on the x-axis is the retention time and plotted on the y-axis a signal (for example obtained by a spectrophotometer, mass spectrometer or a variety of other detectors) corresponding to the response created by the analytes exiting the system. In the case of an optimal system the signal is proportional to the concentration of the specific analyte separated.
  • A chromatograph is equipment that enables a sophisticated separation, e.g. gas chromatographic or liquid chromatographic separation.
  • Chromatography is a physical method of separation that distributes components to separate between two phases, one stationary (stationary phase), the other (the mobile phase) moving in a definite direction.
  • The eluate is the mobile phase leaving the column.
  • The eluent is the solvent that carries the analyte.
  • An eluotropic series is a list of solvents ranked according to their eluting power.
  • An immobilized phase is a stationary phase that is immobilized on the support particles, or on the inner wall of the column tubing.
  • The mobile phase is the phase that moves in a definite direction. It may be a liquid (LC and Capillary Electro chromatography (CEC)), a gas (GC), or a supercritical fluid (supercritical-fluid chromatography, SFC). The mobile phase consists of the sample being separated/analyzed and the solvent that moves the sample through the column. In the case of HPLC the mobile phase consists of a non-polar solvent(s) such as hexane in normal phase or a polar solvent such as methanol in reverse phase chromatography and the sample being separated. The mobile phase moves through the chromatography column (the stationary phase) where the sample interacts with the stationary phase and is separated.
  • Preparative chromatography is used to purify sufficient quantities of a substance for further use, rather than analysis.
  • The retention time is the characteristic time it takes for a particular analyte to pass through the system (from the column inlet to the detector) under set conditions. See also: Kovats' retention index
  • The sample is the matter analyzed in chromatography. It may consist of a single component or it may be a mixture of components. When the sample is treated in the course of an analysis, the phase or the phases containing the analytes of interest is/are referred to as the sample whereas everything out of interest separated from the sample before or in the course of the analysis is referred to as waste.
  • The solute refers to the sample components in partition chromatography.
  • The solvent refers to any substance capable of solubilizing another substance, and especially the liquid mobile phase in liquid chromatography.
  • The stationary phase is the substance fixed in place for the chromatography procedure. Examples include the silica layer in thin layer chromatography
  • The detector refers to the instrument used for qualitative and quantitative detection of analytes after separation.

Chromatography is based on the concept of partition coefficient. Any solute partitions between two immiscible solvents. When we make one solvent immobile (by adsorption on a solid support matrix) and another mobile it results in most common applications of chromatography. If the matrix support, or stationary phase, is polar (e.g. paper, silica etc.) it is forward phase chromatography, and if it is non-polar (C-18) it is reverse phase.