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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] |
Chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a column, a capillary tube, a plate, or a sheet) on which a material called the ''stationary phase'' is fixed. Because the different constituents of the mixture tend to have different affinities for the stationary phase and are retained for different lengths of time depending on their interactions with its surface sites, the constituents travel at different apparent velocities in the mobile fluid, causing them to separate. The separation is based on the differential partitioning between the mobile and the stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase and thus affect the separation. Chromatography may be preparative or analytical. The purpose of preparat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Performance Liquid Chromatography
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pass a pressurized liquid solvent containing the sample mixture through a column filled with a solid adsorbent material. Each component in the sample interacts slightly differently with the adsorbent material, causing different flow rates for the different components and leading to the separation of the components as they flow out of the column. HPLC has been used for manufacturing (''e.g.'', during the production process of pharmaceutical and biological products), legal (''e.g.'', detecting performance enhancement drugs in urine), research (''e.g.'', separating the components of a complex biological sample, or of similar synthetic chemicals from each other), and medical (''e.g.'', detecting vitamin D levels in blood serum) purposes. Chrom ... [...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 c ... [...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, re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 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 ''D'' (separation response), ''Ip'' (performance index) or ''Sm'' (informational en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a column, a capillary tube, a plate, or a sheet) on which a material called the ''stationary phase'' is fixed. Because the different constituents of the mixture tend to have different affinities for the stationary phase and are retained for different lengths of time depending on their interactions with its surface sites, the constituents travel at different apparent velocities in the mobile fluid, causing them to separate. The separation is based on the differential partitioning between the mobile and the stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase and thus affect the separation. Chromatography may be preparative or analytical. The purpose of preparat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
