Small particle liquid chromatography

The effects of flow nonuniformities, in particular, can be severe in gas systems when the ratio of bed-to-particle diameters is small in liquid systems when viscous fingering occurs as a result of large viscosity gradients in the adsorption bed when very small particles (<50 Im) are used, such as in high performance liqmd chromatography systems and in large-diameter beds. A lower bound of the axial... 

High-pressure liquid chromatography (HPLC) is a variant of the simple column technique, based on the discovery that chromatographic separations are vastly improved if the stationary phase is made up of very small, uniformly sized spherical particles. Small particle size ensures a large surface area for better adsorption, and a uniform spherical shape allows a tight, uniform packing of particles. In practice, coated Si02 microspheres of 3.5 to 5 fxm diameter are often used. 

The small peak volumes typical of samples eluted from small bore columns and short small diameter particle columns used in high-speed liquid chromatography place severe demands on the dispersion characteristics of all components of the liquid chromatograph. The standard deviation of a peak eluting from a column is given by... 

Virtually all current research in SFC utilizes either small bore packed columns with particles of 5-10 micrometers in diameter optimized for use in liquid chromatography or narrow bore, fused silica open tubular columns with Immobilized phases similar to those used in gas chromatography. In the latter case columns of saaller internal diameter, 10-100 micrometers, shorter lengths (generally less than 20 m with 1-10 m being the most common length), and more firmly crosslinked stationary phases are used by coaparison with standard columns for gas chromatography. In all... 

Modern high-performance liquid chromatography has been developed to a very high level of performance by the introduction of selective stationary phases of small particle sizes, resulting in efficient columns with large plate numbers per litre. 

Many nonvolatile and thermally labile allelochemicals can be well separated by liquid chromatography (LC). Identification of the separated components on-line by mass spectrometry (MS) is of great value. Fused-silica LC columns of 0.22 mm ID packed with small-particle material are used in the described LC/MS system. The shape of the column end allows direct connection to a electron impact ion source of a magnetic sector mass spectrometer. Separations by LC are reported and LC/MS mass spectra are shown for monoterpenes, diterpene acids, phenolic acids and cardiac glycosides. The LC/MS system provides identification capability and high-efficiency chromatography with a universal detector. 

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