Special Aspects and Problems

After two decades of quantitative l.c. analyses, it has been established that, when proper precautions are taken, these methods can provide accurate and reproducible results.Quantitative l.c. measurements are usually as accurate as, and often more precise than, those obtained by spectrophotometric, paper-chromatographic, and gas-liquid-chro-matographic methods. Both external and internal standardization have been used to translate peak height or areas into quantitative, solute-concentration values. Because peak heights are easy to measure, many methods use this parameter, and, when slightly overlapping peaks or unsteady baselines are encountered, it is the method of choice. With introduction of 

Post-Coiunui Reagents for Enhancing the Detectability of Carbohydrates 

The separative power of l.c. can be coupled to various types of instruments in order to obtain additional qualitative information about eluted compounds. Two such instruments that may be coupled to l.c. include n.m.r. and mass spectrometers. Although there has been one report on the use of l.c.-n.m.r. spectroscopy in carbohydrate research, it is the 

An alternative to direct liquid introduction is the moving belt, or moving-wire, transport interface. Because all l.c. solvents are evaporated before the sample is transported into the ion source, fewer restrictions are placed on solvent type, flow rates, or buffer composition. This system has been used for analysis of mixtures of pentoses, hexoses, and disaccha-rides.  

Most of the direct and indirect (transport) interfaces described here use chemical ionization (c.i.) ion-sources, which are not well suited to such polar, non-volatile compounds as tri- and higher oligosaccharides. The thermospray interface, which can operate on an ion-evaporative mode, is capable of producing intact molecular ions from such nonvolatile, polar molecules and should be useful in oligosaccharide analysis. Molecules of this type, however, can also be easily analyzed by fast-atom-bombardment ionization, and use of this technique, coupled to direct liquid introduction and moving-belt interfaces, has been reported. The latter system has been applied to complex oligosaccharide analysis.  

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