Silica Kieselguhr

The oxidation reaction is interrupted by the addition of 10 ml of ethanol. After 10 min, the manganese dioxide is filtered off through a layer of water-washed fumed silica ( Kieselguhr , Fluka AG Switzerland) and washed with a small amount of sodium bicarbonate (1% solution). The aqueous phase is extracted with 2 x 50 ml of diethyl ether, the ether in turn is extracted with 15 ml of sodium bicarbonate (1% solution) and, after adjustment of the pH to 6.5 with 9M sulfuric acid, the combined aqueous extracts are evaporated to a small volume (30 ml). 

Thin layers. Electrophoretic studies can also be carried out on thin layers of silica, kieselguhr and alumina. As in TLC studies the studies with these materials offer the same advantages of speed and resolution when compared with paper. These materials find their greatest application in combined electrophoretic-chromatography studies in the two-dimensional separations of proteins and nucleic acid hydrolysates. 

Figure 1.4 Silica materials that have been used catalyst support, (a) Natural silica, kieselguhr ( 20 m g ) (b) silica gel ( 500 m g )l and (c) ordered mesoporous silica, SBA-15 ( -500 m g- ).

Selection of stationary phases is, therefore, limited for these preparative techniques. The only materials which can be used are those for which an additional amount of binder endows the necessary stability and does not impair the separation these can be silica, kieselguhr, alumina, plaster of Paris (76), and their combinations. In general, silica gel of TLC quality (15 pm average particle size) with gypsum binder is used with additional binder, 3.5% calcium sulfate hemihydrate. If other types of silica without binder are used, approximately 20% of the binder must be added. It is reconunended that several layers be prepared together and stored in a safe place. They can be activated before use. Precoated glass rotors (1,2, or 4 mm layer thickness) are available from Analtech (Newark, Delaware, USA). 

For example, zeolites are used in different processes, but especially in the catalytic and thermal cracking to produce gasoline from petroleum. Another example is a well-known powdered catalyst of iron-silica (kieselguhr) promoted with K, applied in the Fischer-Tropsch synthesis to obtain hydrocarbons, in a wide range of light hydrocarbons, gasoline, and diesel. 

Note The reagent can be employed on silica gel, kieselguhr, polyamide, RP, CN, NH2 and cellulose layers. 

Note The dipping solution, which can also be used as a spray solution, can be employed with silica gel, kieselguhr, cellulose, RP, NH2 and CN phases. Sugars (exceptions include, for example, fructose, melezitose and raffinose) yield brilliantly colored zones on an almost colorless background when the spray solution is employed. Aldohexoses appear brown, aldopentoses bright red and hexuronic acids orange in color [3]. The detection limit differs for different substances it ranges from 10 ng (pyridoxal) over 100 ng (cinnamaldehyde) up to 2 pg (citral). 

The reagent can be employed on silica gel, kieselguhr and Si 50 000 layers and, if necessary, on RP-2 and RP-8 phases. It cannot be used on RP-18 layers [9] because here the whole plate is fluorescent. )... 

Note The reagent can be employed on silica gel, kieselguhr, RP and, with lower sensitivity of detection, on cellulose layers. The color differentiation is probably greater on cellulose layers [1]. A dark blue background is produced on polyamide layers. 

Note Silica gel, kieselguhr and polyamide layers can be used as stationary phases. Not all acids are stained on RP layers. Amino layers yield a pale blue background. The detection limits are in the pg range for carboxylic acids [1], thioglycolic and dithioglycolic acids [2] and for antithyroid pharmaceuticals [4] they are about 5 ng per chromatogram zone for sterols and steryl esters [6]. 

The reagent can be applied to silica gel, kieselguhr. Si 50 000, RP and CN layers. The detection sensitivity is reduced by a factor of 100 on cellulose layers NH2 layers are not suitable, as would be expected. 

The reagent can be employed on cellulose, silica gel and polyamide layers [11] kieselguhr, RP and Si 50 000 layers are also suitable. 

The layers with which the reagent can be employed include silica gel, kieselguhr. Si 50000 and cellulose. 

Note The reagent can be applied to silica gel, Si 50000 and kieselguhr layers. 

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