Adsorbents graded

Graded Adsorbents and Solvents. Materials used in columns for adsorption chromatography are grouped in Table 12 in an approximate order of effectiveness. Other adsorbents sometimes used include barium carbonate, calcium sulfate, calcium phosphate, charcoal (usually mixed with Kieselguhr or other form of diatomaceous earth, for example, the filter aid Celite) and cellulose. The alumina can be prepared in several grades of activity (see below). 

Graded Adsorbents and Solvents. Some materials used in columns for adsorption... 

As usual, spectral grade adsorbates (benzene, ethylbenzene, p-xylene, and pyridine) were employed (e.g., from Merck, Darmstadt, Germany). They must be further purified via distillation, passage through an alumina column to remove, particularly from ethylbenzene, contaminating oxygenates, subjected to three freeze-pump-thaw cycles and, finally, stored over highly (at 525 K under 10 Pa) activated 4A molecular sieves. These previously activated zeolite A samples were employed to remove even traces of water ampoules with... 

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