|Multi-dimensional liquid chromatography of complex mixtures
|Comprehensive Chromatography - The State of the Art
|University of Amsterdam
Abstract Information :
Liquid chromatography (LC) is a well-established, robust and reliable analytical separation technique. It is pervasively applied to address a wide variety of analytical questions. However, LC is not inherently a high-resolution technique. The 100,000 theoretical plates that can routinely be obtained by gas chromatography or capillary electrophoresis can only be obtained in LC at the expense of relatively long analysis times. This feeds into the need for hyphenated system. On-line sample-preparation techniques and hyphenated detection methods, such as LC-MS, reduce the burden on the LC separation. Alternatively, we can strive to increase the separation power of LC.
One of the best ways to achieve the latter is comprehensive two-dimensional liquid chromatography (LCxLC). This technique has several major advantages. It provides high peak capacities (up to ca. 10,000, as compared to 1,000 for conventional one-dimensional LC), additional selectivity and, in many cases, structured and readily interpretable chromatograms. LCxLC is a highly worthwhile approach, provided that incompatibility issues (the effluent of the first-dimension separation is, in principle, the injection solvent of the second-dimension separation) can be overcome and that method development is adequate and efficient.
Potentially, LCxLC separations may also be performed in a "spatial" mode, using a flat-bed stationary phase, development in the first dimension ("separation in space") and elution in the second and final dimension ("separation in time", hence xLCxtLC). Because all second-dimension separations are performed simultaneously, spatial LCxLC, when implemented successfully, is expected to outperform conventional, column-based LCxLC.
The real challenge, with great potential rewards, is to perform spatial three-dimensional LC separations (xLCxxLCxtLC). Analytes are separated "in space" (i.e. based on their x-y coordinates after the first two separations), followed by elution in the z-direction. For extremely complex samples, with many thousands of relevant analytes, spatial three-dimensional LC is ultimately the way to go, with predicted peak capacities of the order of one million.
In this presentation, the advantages and practical application of column-based LCxLC will be demonstrated based on examples from (industrial) practice and progress towards spatial two- and three-dimensional spatial chromatography will be discussed.