Search results
Results from the WOW.Com Content Network
In chromatography, the retardation factor (R) is the fraction of an analyte in the mobile phase of a chromatographic system. [1] In planar chromatography in particular, the retardation factor R F is defined as the ratio of the distance traveled by the center of a spot to the distance traveled by the solvent front. [2]
The response factor can be expressed on a molar, volume or mass [1] basis. Where the true amount of sample and standard are equal: = where A is the signal (e.g. peak area) and the subscript i indicates the sample and the subscript st indicates the standard. [2]
Thin-layer chromatography (TLC) is a chromatography technique that separates components in non-volatile mixtures. [ 1 ] It is performed on a TLC plate made up of a non-reactive solid coated with a thin layer of adsorbent material. [ 2 ]
Retention distance, or R D, is a concept in thin layer chromatography, designed for quantitative measurement of equal-spreading of the spots on the chromatographic plate and one of the Chromatographic response functions. It is calculated from the following formula:
Another function is the multispot response function (MRF) as developed by De Spiegeleer et al.{Analytical Chemistry (1987):59(1),62-64} It is based also of differences product. This function always lies between 0 and 1. When two RF values are equal, it is equal to 0, when all RF values are equal-spread, it is equal to 1.
So what does this mean? It means that to increase resolution of two peaks on a chromatogram, one of the three terms of the equation need to be modified. 1) N can be increased by lengthening the column (least effective, as doubling the column will get a 2 1/2 or 1.44x increase in resolution). 2) Increasing k' also helps.
The relative mobility (called Rf value or Rm value) is defined as the distance migrated by the protein band divided by the distance migrated by the buffer front. The distances are each measured from the beginning of the separation gel. The migration of the buffer front roughly corresponds to the migration of the dye contained in the sample buffer.
Chromatographic peak resolution is given by = + where t R is the retention time and w b is the peak width at baseline. The bigger the time-difference and/or the smaller the bandwidths, the better the resolution of the compounds.