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The van Deemter equation in chromatography, named for Jan van Deemter, relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation. [1] These properties include pathways within the column, diffusion (axial and longitudinal), and ...
Reversed-phase liquid chromatography (RP-LC) is a mode of liquid chromatography in which non-polar stationary phase and polar mobile phases are used for the separation of organic compounds. [1][2][3] The vast majority of separations and analyses using high-performance liquid chromatography (HPLC) in recent years are done using the reversed ...
A faster flow rate of the eluent minimizes the time required to run a column and thereby minimizes diffusion, resulting in a better separation. However, the maximum flow rate is limited because a finite time is required for the analyte to equilibrate between the stationary phase and mobile phase, see Van Deemter's equation.
The mobile phase composition does not have to remain constant. A separation in which the mobile phase composition is changed during the separation process is described as a gradient elution. [38] [39] For example, a gradient can start at 10% methanol in water, and end at 90% methanol in water after 20 minutes.
Bartel Leendert van der Waerden. Jan Jozef van Deemter (31 March 1918 – 10 October 2004) was a Dutch physicist and engineer known for the Van Deemter equation in chromatography. [1] [2] [3] He obtained his doctorate in physics from the University of Amsterdam in June of 1950. Starting in 1947 he began work for Royal Dutch Shell as a ...
Retardation factor. 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 RF is defined as the ratio of the distance traveled by the center of a spot to the distance traveled by the solvent front. [2]
Paper chromatography is an analytical method used to separate coloured chemicals or substances. [1] It is now primarily used as a teaching tool, having been replaced in the laboratory by other chromatography methods such as thin-layer chromatography (TLC). The setup has three components. The mobile phase is a solution that travels up the ...
A theoretical plate in many separation processes is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other. Such equilibrium stages may also be referred to as an equilibrium stage, ideal stage, or a theoretical tray. The performance of many separation ...