Impregnated adsorbents

The dipping unit can also be employed to impregnate adsorbent layers. It is easy in this way to produce tungstate- [127] or silver nitrate-impregnated layers for separating oligosaccharides or unsaturated compounds. 

Phosphomolybdic acid essential oil components stabilization of the silver nitrate-impregnated adsorbent layer [207]... 

Silica gel plates are modified to form a reversed-phase sorbent by being impregnated with liquid paraffin, silicone oil, or fats. Reversed-phase plates of this type are used in the identification of steroid hormones [8,9]. Table 3.2 lists various other substances that have been used for impregnation [10,11]. Sorbents that are impregnated with amminium oxalate, ammonium sulfate, magnesium acetate, sodium acetate, and silver nitrate have one time or the other been commerically available. As an example, impregnated adsorbents have been used for the resolution of sulfa drugs [19]. 

Individual olefin isomers are generally much better separated on silver-impregnated adsorbents, and Table 7-2 provides several examples. Any factor which increases the stability of the olefin-silver ion complex will increase sample adsorption. For example cis olefins generally form much... 

The interaction of olefins with silver ions on the adsorbent surface can be classified as a rapidly reversible, weak chemisorption. Proton-substituted acetylene derivatives (R—C=C—H) adsorb on silver-impregnated adsorbents with strong, slowly reversible chemisorption (as the silver acetylide). This permits the clean-cut separation of such acetylene compounds (as a group) from other sample components (90). 

This explains why the C02 adsorption capacity of PEI-MPS increases as temperature increases from 25 to 75 oC. However, the reaction between amine groups and C02 is exothermal, therefore, the further temperature increases, the slower C02 adsorption becomes. At a certain temperature, the reaction (1) starts shifting to left side, which accelerates the decomposition of adsorption product and is apply to desorb C02 and regenerate adsorbent. This is the reason why the C02 adsorption capacity of PEI-MPS deceases as temperature increases to 100 and 110 oC. In fact, PEI impregnated adsorbents are usually regenerated at a temperature above 100 oC. 

For analysts not wishing to deal with media preparation, prepackaged sterile media are commercially available. These usually consist of sterile Petri plates containing media-impregnated adsorbent disks (pads). When ready for use, sterile water is added to rehydrate the medium (see Appendix A for cost comparisons). 

This table could be considerably extended since many stationary phases of GC could be in principle adapted. Firm 11 (catalogue No. 9, spring 1965) has made a compilation. Some ready impregnated adsorbents, such as silica gel, impregnated with silanes as described by Kaijfmann, are likewise commercially available (Firms 11, 88). 

The first publications on the separation of lipids on silvernitrate-impregnated adsorbent columns [207] and layers [6, 136, 208] appeared in 1962/63. Argentation-TLC quickly gained favour and has become one of the indispensable aids in the chemistry of lipophilic natural products. 

A dipping apparatus can also be employed to impregnate adsorbent layers with a detection reagent prior to sample application. This preimpregnation method has been used successfully with silver nitrate and phosphomolybdic acid. 

Impregnated adsorbents provide a combination of ad.sorption and chemical reaction to remove traces of specific impurities from gas streams. The process is used to remove impurities that are adsorbable the presence of a reactive chemical in the pores of the adsorbent serves to lock adsorbed material in place, increasing the capacity of the bed and decreasing the vapor pressure of the adsorbate to essentially zero. 

In another commercial application, which is described by Rowley and Lawlor (1984), Calgon Type IVP carbon is used to remove traces of hydrogen sulfide and other sulfur compounds from gases vented from tanks and storage pits of a Stretford natural gas treating plant. The impregnated adsorbent bed is 3 ft deep and is operated in the upflow mode. 

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