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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]
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.
In contrast to the similar concept called Retention uniformity, R d is sensitive to R f values close to 0 or 1, or close to themselves. If two values are not separated, it is equal to 0. For example, the R f values (0,0.2,0.2,0.3) (two compounds not separated at 0.2 and one at the start ) result in R D equal to 0, but R U equal to 0.3609. When ...
The spot capacity (analogous to peak capacity in HPLC) can be increased by developing the plate with two different solvents, using two-dimensional chromatography. [8] The procedure begins with development of a sample loaded plate with first solvent. After removing it, the plate is rotated 90° and developed with a second solvent.
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] This is called the stationary phase. [2]
In liquid chromatography, the mobile phase velocity is taken as the exit velocity, that is, the ratio of the flow rate in ml/second to the cross-sectional area of the ‘column-exit flow path.’ For a packed column, the cross-sectional area of the column exit flow path is usually taken as 0.6 times the cross-sectional area of the column.
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.