Chromatographic considerations

The principal assets of LC/NMR are speed of analysis, particularly for con ilex mixtures, and the freedom from the impurity peaks generally associated with ihe chromatographic purification of low-level components. Its principal drawbacks are the restrictions on chromatographic loadings and the presence of protic solvents, which may both lead to restrictions in the amount and type of data which can be obtained. The corollary of these drawbacks is that some chromatographic expertise is required to get the most out of the technique. 

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Jenkins T., Davidson G, PoliakofFM., Comparison ofXe and COi as Mobile Phase in On-Line SFC-FTIR Chromatographic Considerations, Journal of High Resolution Chromatography, Vol. 15, pp. 819-826, 1992... 

Chromatographic Considerations. The experimental problem is now reduced to the far from trivial one of determining the ratio of the retention volumes of the two isotopically substituted molecules. Consider a typical chromatogram for two difficultly resolvable isomers such as is sketched in Figure 1. Here to is the time from injection that a completely inert nonadsorbed material is eluted t2 and ti are the corrected retention times P2/P1 = ti/t2) (21) t is the average residence time in the column and tv is the peak width. 

Compound 15 was first identified in Osmanthus asiaticus, a plant of Oleaceae family [15]. Compound 16 was isolated in Primus grayana, a plant of rosaceae family [16] and in Ricciocarpus natans, Ricciaceae [17]. Compound 17 was assumed to be present in O. europaea [18,19], on the basis of chromatographic considerations and was identified [14], together with 15 and 16[14], in carolea cultivar. 

D.W. Armstrong, T. Ward and A. Berthod, Micellar Effects on Molecular Diffusion Theoretical and Chromatographic Considerations, Anal Chem., 58 579 (1986). 

Location Ensure appropriate floor space and bench space is available for the instrument and all ancillary equipment (i.e., gas chromatograph, elemental analyzers, and interfaces) and also future equipment that may be purchased to interface with the IRMS, for example, a liquid chromatograph. Consideration should also be given to the required space for conducting maintenance on the instrument and easy access to all components. 

This book serves two separate and important functions for the chromatographen practical and operational. The first duee chapters deal with the opoational aspects of solvents. They contain information regarding solvents and solvent classes, method optimization techniques, and the definition and use of method validation proto-cols/system suitability parameters. These chapters describe solvents from a practical use-oriented point of view. Here the physical and chemical properties of numerous solvents are discussed with respect to their impact on the chromatographic system. A clear understanding of the implications presented by these properties will save the chromatographer considerable time and effort. 

Guidelines for the selection of column diameter, film thickness of stationary phase, and length will now be established on the basis of practical gas chromatographic considerations. 

Other chromatographic considerations, outlined below, should be considered when designing an HPLC separation method. 

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