Chromatography Mobile phases Stationary

Type of Chromatography Mobile Phase Stationary Phase... 

In chromatography there are at least three equilibria analyte/mobile phase, analyte/stationary phase and mobile phase/stationary phase. The origin of the term theoretical plate in chromatography comes from the adaptation of an older plate theory for distillation described by Martin and Synge (Nobel Prize for Chemistry, 1952). This term which is universally used for historical reasons, has no physical significance. It may have been preferable to call it a Tswett ... 

Chromatography Mobile phase Gas Stationary phase Liquid Configuration Column... 

Several kinds of flavonoids are efficiently separated and analyzed using packed or capillary column supercritical fluid chromatography. The composition of mobile phase, stationary phase, temperature, and pressure aU affect the resolution. This article mainly focuses on the separation of polymethoxylated flavones, polyhydroxyl flavonoids, and flavonol isomers. 

Supercritical pSFC applications can be defined as those in which the mobile phase is a single substance heated and pressurized above its critical point. Carbon dioxide has overwhelmingly been the compound of choice for these mobile phases. Stationary phases typically used for these applications have been polymeric materials or polymer-coated porous silica. Chromatography on uncoated silica-based stationary phases with CO2 has, in general, been unsuccessful. 

Typical thin-layer separations are performed on a glass plate that is coated with a thin and adherent layer of finely divided particles this layer constitutes the stationary phase. The particles are similar to those described in the discussion of adsorption, normal- and reversed-phase partition, ion-exchange, and size-exclusion column chromatography. Mobile phases are also similar to those employed in high-performance liquid chromatography. 

In a chromatographic phase system, there are at least three sets of equilibria solute/mobile phase, solute/stationary phase and mobile phase/stationary phase. In a more recent theory of chromatography, no consideration is given to the idea of molecules immobilized by the stationary phase but rather that were simply slowed down when passing in close proximity. 

In a particular partition chromatography column, the volumes of mobile phase, stationary phase, and inert phase are in the ratio A, A/ of 0.20 0.05 0.75 and the HETP is 0.0050 cm. Two substances having partition coefficients of 1.50 and 1.55 are to be separated. Calculate (a) the values for the two substances, (b) the volume of eluent required to bring each of the bands in turn to a point 10.0 cm down a column of total area 1.0 cm, (c) the volume of eluent required to wash all but 0.13% of the leading component from a 30 cm column, and (d) the % of the lagging component that has been removed under the conditions of part c. 

Column chromatography mobile phase flows through a column containing the stationary phase material, either as a particulate packing or as a film on the inner wall (WCOT) of the column tubing. 

Of the various forms of liquid chromatography, that involving ion exchange would seem to be most amenable to a precise phyncochemical description since the mobile-phase/stationary-phase interaction amounts simply to displacement of one (matrix-bound) ion by another. However, the effects introduced by charged species render such systems even more intractable than is the case with non-electrolyte solutions. Nevertheless, we show in what follows that a rigorous expression can be written for the relevant equilibrium constant, and that this can be related directly to chromatographic retentions. 

An RP-TLC system with tertiary mobile phase [stationary phase RP-18 E254s mobile phase water-methanol-tetrahydrofuran (5 2 3, v/v/v) applied twice] was used in the analysis of taxoid fractions obtained after highspeed countercurrent chromatography (HSCCC) isolation and was suitable for paclitaxel and cephalomannine qualitative determination. ... 

Mobile phase Stationary phase Types of chromatography " Abbreviation Separation... 

Analytical separations may be classified in three ways by the physical state of the mobile phase and stationary phase by the method of contact between the mobile phase and stationary phase or by the chemical or physical mechanism responsible for separating the sample s constituents. The mobile phase is usually a liquid or a gas, and the stationary phase, when present, is a solid or a liquid film coated on a solid surface. Chromatographic techniques are often named by listing the type of mobile phase, followed by the type of stationary phase. Thus, in gas-liquid chromatography the mobile phase is a gas and the stationary phase is a liquid. If only one phase is indicated, as in gas chromatography, it is assumed to be the mobile phase. 

In their original theoretical model of chromatography, Martin and Synge treated the chromatographic column as though it consists of discrete sections at which partitioning of the solute between the stationary and mobile phases occurs. They called each section a theoretical plate and defined column efficiency in terms of the number of theoretical plates, N, or the height of a theoretical plate, H where... 

In gas chromatography (GC) the sample, which may be a gas or liquid, is injected into a stream of an inert gaseous mobile phase (often called the carrier gas). The sample is carried through a packed or capillary column where the sample s components separate based on their ability to distribute themselves between the mobile and stationary phases. A schematic diagram of a typical gas chromatograph is shown in Figure 12.16. 

The most widely used particulate support is diatomaceous earth, which is composed of the silica skeletons of diatoms. These particles are quite porous, with surface areas of 0.5-7.5 m /g, which provides ample contact between the mobile phase and stationary phase. When hydrolyzed, the surface of a diatomaceous earth contains silanol groups (-SiOH), providing active sites that absorb solute molecules in gas-solid chromatography. 

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