ANYL 358 |
| For the separation of mixtures of extremely high complexity and/or for the development of generic methods (e.g. in drug discovery), high peak capacities are required. Although recent developments in fluid based separation techniques i.e. high pressure and elevated temperature, drastically increase the column efficiencies and thus the peak capacity, comprehensive techniques in which two separation mechanisms are hyphenated are much more powerful to obtain high peak capacities. Of all combinations of separation mechanisms, coupling of normal phase (NP) LC to reversed phase (RP) LC is without any doubt the most orthogonal in nature for the separation of small molecules. The most widely used interface at present is a two position/ten port switching valve, equipped with two storage loops of which the volume corresponds to the mobile phase quantity per minute eluting from the first dimension. Generally, fractions of 1 minute are trapped, hereby necessitating a RP analysis and regeneration time of 1 minute. A new type of interface was designed, doubling the analysis and regeneration time in the second dimension. Through the addition of extra tools (two position/ten port switching valve, detector, pump and second dimension column) the separation range in the second dimension was increased, resulting in higher resolution and overall peak capacity. In order to further diminish interferences originating from mobile incompatibilities in NPLCxRPLC, the set-up was modified to couple supercritical fluid chromatography (SFC) to reversed phase (RP) LC (SFCxRPLC). The figures of merit of the comprehensive systems are discussed and illustrated with the analysis of natural products and pharmaceuticals. Advantages and disadvantages of on-line versus off-line combination are presented. |
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ACS Award in Chromatography in Honor of J. Michael Ramsey
1:30 PM-5:00 PM, Tuesday, August 21, 2007 BCEC -- 104C, Oral
Division of Analytical Chemistry |