Packings and Modes of hplc

The large porous particles are the oldest of these materials, and are no longer used in analytical hplc, although because of their high sample capacity they are still useful in preparative work. Columns packed with the large particles have relatively low efficiencies because of the long time it takes for solute species to diffuse into and out of the porous structure (slow mass transfer). 

Analytical hplc these days is nearly always done with microparticulate column packings, which are small porous particles, usually spherical or irregular silica, with nominal diameters of 3,5 or 10 fxm. They combine the best features of the other two types, having high efficiency as well as a large surface area. In bulk, the appearance of a microparticulate silica resembles that of a fine talcum powder. With microparticulates, dry packing methods result in column beds that are unstable under pressure, so they are packed into columns using a slurry of the material in a suitable solvent and under considerable pressure. 

Type silica silica, ODS bonded, fully end-capped 

Pressure drops were measured in a 25 cm x 4.6 mm column with a 1 cm3 min 1 mobile flow rate using  

You twill find as you get further involved with hplc that there is a bewildering Zariety of microparticulate packings available in the trade literature. The textbook by Hamilton and Sewell (second Edition, Chapter 4) has an extensive list, as do most other textbooks. To keep things in perspective, remember that almost all the work in 

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