Carbohydrates separation techniques

In this sense, HPLC is an analytical method that cannot be put aside in the determination of carbohydrates, since the wide variety of these species and their inherent polydispersity and heterogeneity require separation techniques of high resolving power and high selectivity (7). 

The chronology of the development of the different separation techniques employed for carbohydrate analysis in foodstuffs may be summarized as follows ... 

Ken s geographical transition to the New World was accompanied by a concomitant transition in his research emphasis. Although he maintained an interest in polysaccharide chemistry, the publication record from Queen s University attests to the universality of his interests in carbohydrate chemistry. J. K. made major contributions to synthetic carbohydrate chemistry, stereochemistry, biosynthetic mechanisms, and metabolism of carbohydrates, and the application of such separational techniques as paper and gas-liquid chromatography in the carbohydrate field. The results of his lifetime of research were documented in over 300 scientific publications. Clearly, it would be impractical to review this number of papers individually, and consequently, only a representative sample will be treated. A list of Professor Jones s publications is appended to this article. 

In principle, the same carbohydrates and their degradation products formed after hydrolysis of wood can be recovered from sulfite spent liquors. However, this requires complicated and expensive separation techniques. The industrial use of sulfite spent liquor components is mainly limited to fermentation processes. The most common product is ethyl alcohol which is produced from hexose sugars by yeast (Saccharomyces cerevisae) and separated from the mixture by distillation. Even the carbon dioxide formed in the process can be recovered. Other fermentation products, including acetone, n-butanol, and lactic acid, can be produced by certain microorganisms. Because some contaminants, for example, sulfur dioxide, inhibit the growth of the yeast, they must be removed from the liquor prior to the fermentation. 

In principle, monosaccharides and their conversion products including furfural can be isolated from sulfite spent liquors. Because of the complicated separation technique needed and since alternative raw material sources, such as wood and agricultural wastes are available, these processes have so far been of very limited practical interest. Because of their carbohydrate content, sulfite spent liquors find use either directly or after some fractionation as a feed component for cattle. 

Electrospray mass spectrometry has developed into a well-established method of wide scope and potential over the past 15 years. The softness of electrospray ionization has made this technique an indispensable tool for biochemical and biomedical research. Electrospray ionization has revolutionized the analysis of labile biopolymers, with applications ranging from the analysis of DNA, RNA, oligonucleotides, proteins as well as glycoproteins to carbohydrates, lipids, gly-colipids, and lipopolysaccharides, often in combination with state-of-the-art separation techniques like liquid chromatography or capillary electrophoresis [1,2]. Beyond mere analytical applications, electrospray ionization mass spectrometry (ESMS) has proven to be a powerful tool for collision-induced dissociation (CID) and multiple-stage mass spectrometric (MSn) analysis, and - beyond the elucidation of primary structures - even for the study of noncovalent macromolecular complexes [3]. 

The majority of reports have used electrospray ionization mass spectroscopy (ESI-MS) as an analytical detection method because of its sensitivity and the soft namre of its ionization procedure, which generally only leads to the detection of the molecular ions of the positive library members. Many separation techniques have been coupled to ESI-MS, including affinity chromatography (49), size exclusion chromatography (50, 51), gel filtration (52), affinity capillary electrophoresis (53-58), capillary isoelectric focusing (59), immunoaffinity ultrafiltration (60), and immunoaffinity extraction (61). ESI-MS has also been used alone (62) to screen a small carbohydrate library. Other examples reported alternative analytical techniques such as MALDI MS, either alone (63, 64) or in conjunction with size exclusion methods (65), or HPLC coupled with immunoaffinity deletion (66). 

CE is an analytical separation technique capable of high-resolution separation of a diverse range of chemical compounds and is therefore well suited for metabolomics.17,64 It is particularly suitable for the separation of polar and charged compounds and compounds with widely different structures, functional groups, physiochemical properties, and concentrations, for example, organic acids, amino acids, nucleic acids, steroids, carbohydrates, and flavonoids in various matrices. CE is complementary to GC and HPLC, and in many cases, samples that cannot be... 

MS, especially in combination with advanced separation techniques, is one of the most powerful and versatile techniques for the structural analysis of bacterial glycomes. Modern mass spectral ionization techniques such as electrospray (ESI) and matrix-assisted laser desorption/ionization (MALDI) provide detection limits in the high atto- to low femto-mole range for the identification of peptides and complex carbohydrates. Structural characterization of these trace level components can be achieved using tandem MS. This provides a number of specific scanning functions such as product, precursor ion, and constant neutral loss scanning to... 

LC is the most widely used of all of the analytical separation techniques. The reasons for the popularity of the method are its sensitivity, its ready adaptability to accurate quantitative determinations, its case of automation, its suitability for separating nonvolatile species or thermally fragile ones, and above all. its widespread applicability to substances that are important to industry, to many fields of science, and to the public. Examples of such materials include amino acids, proteins, nucleic acids, hydrocarbons, carbohydrates, drugs, terpenoids, pesticides, antibiotics, steroids, inetal-organic species, and a variety of inorganic substances,... 

Precolumns can also be used to condition the mobile phase. In this case they are usually operated in a position upstream from the sample injection point. For example, a silica column loaded with a large amount of amine modifier can be used to equilibrate the mobile phase with the amine modifier. This technique has been employed in carbohydrate separations on silica columns that are dynamically coated with an amine modifier. Silica columns have been used to saturate the mobile phase with silica in an attempt to prolong the column life of silica-based columns in alkaline mobile phases. That this technique actually works has, however, not yet been demonstrated unambiguously. 

Numerous research papers and reviews on carbohydrate separations by CE have been written for the past several years. Researches have successfully addressed problems, such as tremendous diversity and complexity of this class of compounds, polar and neutral nature of most carbohydrates, their low ultraviolet (UV) extinction coefficients, and lack of functional groups. In the previous edition of this book, Olechno and Nolan [16] published a comprehensive overview of the CE separation techniques, attempted and developed for intact and derivatized carbohydrates, charged and neutral, as well as detection approaches by UV, indirect fluorescence, electrochemical (e.g., amperometric) detection, refractive index, and laser-induced fluorescence (LIE). A variety of buffer systems were... 

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