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Retention Uniformity
Retention uniformity, or ''RU'', is a concept in thin layer chromatography. It is designed for the quantitative measurement of ''equal-spreading'' of the spots on the chromatographic plate and is one of the Chromatographic response functions. Formula Retention uniformity is calculated from the following formula: R_ = 1 - \sqrt{\frac{6(n+1)}{n(2n+1)}\sum_{i=1}^{n}{\left(R_{Fi}-\frac{i}{n+1}\right)^2 where ''n'' is the number of compounds separated, ''Rf (1...n)'' are the Retention factor In chromatography, the retardation factor (''R'') is the fraction of an analyte An analyte, component (in clinical chemistry), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The purest ... of the compounds sorted in non-descending order. Theoretical considerations The coefficient lies always in range and 0 indicates worst case of separation (all Rf values equal to 0 or 1), value 1 indicates ideal equal-spreading of the spot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thin Layer Chromatography
Thin-layer chromatography (TLC) is a chromatography technique used to separate non-volatile mixtures. Thin-layer chromatography is performed on a sheet of an inert substrate such as glass, plastic, or aluminium foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide (alumina), or cellulose. This layer of adsorbent is known as the stationary phase. After the sample has been applied on the plate, a solvent or solvent mixture (known as the mobile phase) is drawn up the plate via capillary action. Because different analytes ascend the TLC plate at different rates, separation is achieved. It may be performed on the analytical scale as a means of monitoring the progress of a reaction, or on the preparative scale to purify small amounts of a compound. TLC is an analytical tool widely used because of its simplicity, relative low cost, high sensitivity, and speed of separation. TLC functions on the same principle as all chromatography: a com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatographic Response Function
Chromatographic response function, often abbreviated to CRF, is a coefficient which measures the quality of the separation in the result of a chromatography. The CRF concept have been created during the development of separation optimization, to compare the quality of many simulated or real chromatographic separations. Many CRFs have been proposed and discussed. In high performance liquid chromatography the CRF is calculated from various parameters of the peaks of solutes (like width, retention time, symmetry etc.) are considered into the calculation. In TLC the CRFs are based on the placement of the spots, measured as RF values. Examples in thin layer chromatography The CRFs in thin layer chromatography characterize the ''equal-spreading'' of the spots. The ideal case, when the RF of the spots are uniformly distributed in range (for example 0.25,0.5 and 0.75 for three solutes) should be characterized as the best situation possible. The simplest criteria are \Delta R_F and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retention Factor
In chromatography, the retardation factor (''R'') is the fraction of an analyte in the mobile phase of a chromatographic system. 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. Ideally, the values for ''RF'' are equivalent to the R values used in column chromatography. Although the term retention factor is sometimes used synonymously with retardation factor in regard to planar chromatography the term is not defined in this context. However, in column chromatography, the retention factor or capacity factor (''k'') is defined as the ratio of time an analyte is retained in the stationary phase to the time it is retained in the mobile phase, which is inversely proportional to the retardation factor. General definition In chromatography, the retardation factor, ''R'', is the fraction of the sample in the mobile phase at equilibrium, defined as: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retention Distance
Retention distance, or ''RD'', 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: R_D = \Bigg n+1)^ \prod^n_ where ''n'' is the number of compounds separated, ''Rf (1...n)'' are the Retention factor of the compounds sorted in non-descending order, ''Rf0'' = 0 and ''Rf(n+1)'' = 1. Theoretical considerations The coefficient lies always in range and 0 indicates worst case of separation (all Rf values equal to 0 or 1), value 1 indicates ideal equal-spreading of the spots, for example (0.25,0.5,0.75) for three solutes, or (0.2,0.4,0.6,0.8) for four solutes. This coefficient was proposed as an alternative to earlier approaches, such as delta-Rf, delta-Rf product or MRF (Multispot Response Function). Besides its stable range, the advantage is a stable distribution as a random variable, rega ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
