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An R F value will always be in the range 0 to 1; if the substance moves, it can only move in the direction of the solvent flow, and cannot move faster than the solvent. For example, if particular substance in an unknown mixture travels 2.5 cm and the solvent front travels 5.0 cm, the retardation factor would be 0.50.
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.
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:
By definition, the linear relative permittivity of vacuum is equal to 1, [19] that is ε = ε 0, although there are theoretical nonlinear quantum effects in vacuum that become non-negligible at high field strengths. [20] The following table gives some typical values.
A Magic Triangle image mnemonic - when the terms of Ohm's law are arranged in this configuration, covering the unknown gives the formula in terms of the remaining parameters. It can be adapted to similar equations e.g. F = ma, v = fλ, E = mcΔT, V = π r 2 h and τ = rF sinθ.
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.