Carbohydrates adsorption chromatography

In 1903, M. Tswett first applied adsorption chromatography to the separation of plant pigments, using a hydrocarbon solvent and inulin powder (a carbohydrate) as stationary phase. The separation of colored bands led to the name chromatography, from the Greek word chromatos, meaning color." Tswett later found that CaC03 or sucrose also could be used as stationary phases.3... 

Precolumn derivatization has been a widely used resource in adsorption chromatography of carbohydrates, although it alters their related properties and in some cases their detectability. 

One must be cautious in interpreting data on carbohydrates, hydroxyl acids, and uronic acids in humic substances. As Thurman and Malcolm 11983) have pointed out, the amount of these materials in a fulvic acid is a function of the way that it was isolated. They have shown that nonassociated carbohydrates, uronic acids, and hydroxyl acids may be separated from fulvic acid by adsorption chromatography on XAD resins. For example, a prairie soil fulvic acid contained 20% carbohydrate before XAD adsorption chromatography and only 5% after chromatography. In the fulvic acid isolated by Sposito et al. (1978) adsorption chromatography was not used in the purification process and therefore some of the carbohydrate that they report may not be an integral part of the fulvic acid structure. 

The introduction of any new analytical technique seems to inspire its indiscriminate application, without use of proper precautions, to a variety of problems, many of which could be solved more quickly by other methods. It should be emphasized that gas-liquid chromatography is not a panacea for all problems in the analysis of carbohydrate derivatives. Fast, efficient resolution of any given mixture of derivatives requires judicious selection from among the methods of countercurrent partition, liquid-liquid chromatography on columns or paper, adsorption chromatography on columns or thin layers, electrophoresis, and gas-liquid chromatography. The last method is, under the appropriate conditions, a powerful addition to the list because of its high efficiency and rapid operation, and the reliability of both the qualitative and the quantitative results. 

Paper chromatography of amino acids is best described as partition chromatography between the stationary aqueous (most polar) phase in the cellulose fibers and the mobile (least polar) phase formed by the solvent system used. The actual situation is somewhat more complicated. The stationary phase cannot be described as pure water but rather as a concentrated aqueous carbohydrate solution. Elements of adsorption chromatography are involved as shown by the relatively small/ f values for aromatic amino acids and by the possibility of separating enantiomers (mirror images) of amino acids depending on the chirality of the cellulose in the paper. 

Abscisic acid (ABA), 784-785 Absorption measurement, 208 Acid dyes, 1015,1016 Adsorbent gradient, ISO Adsorbents, 17 Adsorption chromatography aluminas and, 17,107 Kowalska model of, 63-64 O ik model of, 61-62 Scott-Kucera model of, 62-63 silica gels and, 17,104 Synder-Soczewinski model of, 60 Alcoholic products, dyes from, 1005 Alkaloids from plants, 1040 pyrrolizidine, 1036-1040 Aluminas, 17,106-107 adsorption chromatography and, 107 partition chromatography and, 107 physical and chemical properties, 106-107 for separation of carbohydrates, 494 Amikacin, 458-461... 

Because of the different interactions involved in partition and adsorption processes, they may be applied to different separation problems. Partition processes are the most effective for the separation of small molecules, especially those in homologous series. Partition chromatography has been widely used for the separation and identification of amino acids, carbohydrates, and fatty acids. Adsorption techniques, represented by ion-exchange chromatography, are most effective when applied to the separation of macromolecules including proteins and nucleic acids. 

Aldonic, uronic, and ascorbic acids, lactones, and N-acetylated amino sugars were separated on sulfonated polystyrene-divinylbenzene, a strong polyanion exchanger (Wheaton and Bauman, 1953). This method is adaptable to neutral carbohydrates without complexation or adsorption, by immersion in strong alkali to ionize the hydroxyl groups (ion chromatography). 

In normal-phase chromatography, polar stationary phases are employed and solutes become less retained as the polarity of the mobile-phase system increases. Retention in normal-phase chromatography is predominately based upon an adsorption mechanism. Planar surface interactions determine successful use of NPC in separation of isomers. The nonaqueous mobile-phase system used in NPC has found numerous applications for extremely hydrophobic molecules, analytes prone to hydrolysis, carbohydrates, and sat-urated/unsaturated compounds. In the future, with the advent of new stationary phases being developed, one should expect to see increasingly more interesting applications in the pharmaceutical industry. 

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