Paper chromatography ascending

The substance having same Revalue can be separated by two dimensional paper chromatography. Descending technique is better because compounds with low Ry-values which cannot be completely separated by ascending method can be separated by descending technique. 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method,... 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method, i.e. the solvent creeps up the stationary phase by capillarity. The adsorbent (e.g. silica, alumina, cellulose) is spread on a rectangular glass plate (or solid inert plastic sheet). Some adsorbents (e.g. silica) are mixed with a setting material (e.g. CaSC>4) by the manufacturers which causes the film to set on drying. The adsorbent can... 

Carboxylic acids often have been identified by means of paper chromatography Clarke and Bazill (10) have extracted plasticizers from polyvinyl chloride first with ether and then with methanol. Subsequently the extracts were saponified with alcoholic potassium hydroxide, and the precipitated potassium salts were isolated and converted into free acids. These, in alcoholic solution, were then applied to paper and chromatographed ascendingly with a mixture of butanol, pyridine, water, and ammonia the migration period was about six hours. A number of additional color tests facilitated identification of unknown acids. 

Fig. 16.29 Separation of polyphosphate anions by paper chromatography. The ions are first allowed lo migrate ki a bask solvent and subsequently in an acidic solvent. The straight-chain polyphosphates lie on the ascending branch of the Y." the meuiphosphates on the lower branch. (From Van Wazer. i. R. Phosphorus and Its Comp,ntnds. Wiley New York. 1958 Vol. (. p 702. Reproduced with per mission.J...

For the separatory determination of pyridoxine in multi-vitamin preparations, other vitamins are separated by paper chromatography in which the upper layer of butanol-ammonium hydroxide-water (4 1 5) are used as the developer, and by the one-dimensional ascending method (102). 

The different methods of arranging the filter paper in the chromatographic chamber have been applied to sugar separations descending, ascending,39 40 and circular or horizontal development.41 These methods and other techniques will be discussed below. Detailed descriptions of the equipment needed for paper chromatography are readily available.8... 

Fig. 7. Water content of paper in ascending chromatography. Paper, Schleicher and Schiill 598 G (data according to Griine, G23) B, water level H, height above water level Q, water content of the strip expressed in percentage of the paper (w/w).

In paper chromatography, 5-anilino-2-mercapto-l,3,4-thiadiazole is used as a reagent in the ascending chromatography of various cations (68RRC909), while 2-amino-1,3,4-... 

Figure 6-8 Ascending thin-layer and paper chromatography.

With paper chromatography a descending technique may be more convenient (though an ascending method can of course also be used). 

Adenine (10 g, 0.074 mol) was dissolved in hot HOAc (60 mL). The solution was then cooled to 20 °C, 30% aq HjOj (37 mL) was added, and the solution was allowed to stand at rt for 2.5 d. At the end of this time a substantial proportion of the product had crystallized. This material (7.0 g) was collected and washed with a little HOAc. Further batches (1,6 and 0.2 g) were collected 3.5 and 4.5 d after the start of the oxidation. These crops each showed single spots on ascending paper chromatography. Further oxide (0.6 g) could be obtained from the final filtrate after destroying the HjOj by the addition of Pd/C and removing some of the HOAc in vacuo. The total yield was 9.4 g (84%). Crystallization of adenine I-oxide from boiling HjO yielded white filamentous crystals decomposition point 297-307°C. 

Figure 21-1. Apparatus required for ascending paper chromatography.

There are several types of paper chromatography, and they are named according to the direction the mobile phase flows through the paper. These are ascending, descending, horizontal, and two-dimensional, and any of these with a reversed phase. 

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