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The particle size of the stationary phase is generally finer in flash column chromatography than in gravity column chromatography. For example, one of the most widely used silica gel grades in the former technique is mesh 230 – 400 (40 – 63 μm), while the latter technique typically requires mesh 70 – 230 (63 – 200 μm) silica gel.
Methods in which the stationary phase is more polar than the mobile phase (e.g., toluene as the mobile phase, silica as the stationary phase) are termed normal phase liquid chromatography (NPLC) and the opposite (e.g., water-methanol mixture as the mobile phase and C18 (octadecylsilyl) as the stationary phase) is termed reversed phase liquid ...
A chromatography column is a device used in chromatography for the separation of chemical compounds. A chromatography column contains the stationary phase , allowing the mobile phase to pass through it.
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 ...
Typical stationary phases for normal-phase chromatography are silica or organic moieties with cyano and amino functional groups. For reversed phase, alkyl hydrocarbons are the preferred stationary phase; octadecyl (C18) is the most common stationary phase, but octyl (C8) and butyl (C4) are also used in some applications. The designations for ...
The most common mode of liquid chromatography is reversed phase, whereby the mobile phases used, include any miscible combination of water or buffers with various organic solvents (the most common are acetonitrile and methanol). Some HPLC techniques use water-free mobile phases (see normal-phase chromatography below).
Greatly unchanged from Tswett's time until the 1940s, normal phase chromatography was performed by passing a gravity-fed solvent through small glass tubes packed with pellicular adsorbent beads. [citation needed] It was in the 1940s, however, that there was a great revolution in gas chromatography (GC).
In normal-phase TLC, the stationary phase is polar. Silica gel is very common in normal-phase TLC. More polar compounds in a sample mixture interact more strongly with the polar stationary phase. [citation needed] As a result, more-polar compounds move less (resulting in smaller R f) while less-polar compounds move higher up the plate (higher R ...
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