Chromatography, general open-column

The literature describes chromatographic techniques related to the characterization, isolation and purification of iridoids. Most reports show the open column technique as the principal technique used to isolate this class. Also, there have been few studies on counterflow and capillary electrophoresis chromatographies. In general, there has been little scientific investment in the area of obtaining iridoids of the Apoc3maceae family, despite the great pharmacological importance of this class of constituents. 

The content of aroma compounds is, in general, low, and compositions of these compounds are often complex. Therefore, at the dawn of analytical chemistry, aroma compounds were extracted from a huge mass of raw material. Fractionation was carried out by means of distillation, and various other classical procedures (e.g., crystallization, pH control in extraction, derivatization) were employed. Quite obviously, compounds revealed using these procedures were inevitably restricted to a set of major constituents, if any. Occasionally, before the 1950s, additional techniques like UV-IR spectroscopy and open-column chromatography were employed and were helpful to some extent. 

The shape of the zone, at least a characteristic of its width, is of major concern in all chromatographic techniques. Jonsson [4] and Giddings [5] seem to discuss the case and peculiarities of open columns in more details than do other general monographs on chromatography. 

The hydrocarbon ("oil") fraction of a coal pyrolysis tar prepared by open column liquid chromatography (LC) was separated into 16 subfractions by a second LC procedure. Low voltage mass spectrometry (MS), infrared spectroscopy (IR), and proton (PMR) as well as carbon-13 nuclear magnetic resonance spectrometry (CMR) were performed on the first 13 subfractions. Computerized multivariate analysis procedures such as factor analysis followed by canonical correlation techniques were used to extract the overlapping information from the analytical data. Subsequent evaluation of the integrated analytical data revealed chemical information which could not have been obtained readily from the individual spectroscopic techniques. The approach described is generally applicable to multisource analytical data on pyrolysis oils and other complex mixtures. 

Virtually all current research in SFC utilizes either small bore packed columns with particles of 5-10 micrometers in diameter optimized for use in liquid chromatography or narrow bore, fused silica open tubular columns with Immobilized phases similar to those used in gas chromatography. In the latter case columns of saaller internal diameter, 10-100 micrometers, shorter lengths (generally less than 20 m with 1-10 m being the most common length), and more firmly crosslinked stationary phases are used by coaparison with standard columns for gas chromatography. In all... 

The first chiral phases introduced for gas chromatography were either amino acid esters, dipeptide, diamide or carbonyl-bis(amino acid ester) phases [721,724,756-758]. In general, these phases exhitdted poor thermal stability and are infrequently used today. Real interest and progress in chiral separations resulted from the preparation of diamide phases grafted onto a polysiloxane backbone. These phases were thermally stable and could be used to prepare efficient open tubular columns [734,756,758-762]. These phases are prepared from commercially available poly(cyano-propylmethyldimethylsiloxanes) or poly (cyanopropylmethylphenyl-... 

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