Anal Bioanal Chem (2004) 378 : 1935 DOI 10.1007/s00216-004-2549-6
E D I TO R I A L
Marja-Liisa Riekkola
Multidimensional separations in analytical chemistry
Published online: 3 March 2004 © Springer-Verlag 2004
It was over 20 years ago that J. Calvin Giddings set out his two criteria for an ideal multidimensional separation: 1) the separation mechanisms must be orthogonal, meaning that the mechanisms must be completely independent in each dimension, and 2) no resolution achieved in the first dimension of separation may be lost in any subsequent dimension. Conventional, heart-cut multidimensional separations are valuable when extra resolution is needed in the examination of a small segment of peaks in a complex chromatogram. Prior knowledge of the sample composition is always beneficial. In comprehensive multidimensional separation techniques, the entire sample, not just a part of it, is subjected to different separations. Typically the resolution is very high. Heart-cutting techniques are normally abbreviated with a hyphen (e.g. LC–LC, LC–GC), while comprehensive multidimensional techniques are indicated with the multiplex sign (×) (e.g. LC×LC, GC×GC). Multidimensional techniques provide high peak capacity, which is essential for the analysis of complex mixtures with numerous components. Sensitivity is much improved as well. The appreciation of these advantages is seen in the continuing growth of publications in the field of multidimensional separations. The best features of sample pretreatment and analytical methods can be combined. On-line coupling of a more or less orthogonal technique like extraction with chromatog-
M.-L. Riekkola (✉) Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 Helsinki, Finland Tel.: +358-9191-50268, Fax: +358-9191-50253, e-mail:
[email protected]
raphy allows high sensitivity, no contamination and easy automation. In this case, continuous elution is not carried out during the first dimension. This special issue deals almost entirely with two-dimensional separation systems. Separation techniques that utilize more than two dimensions can certainly be expected in the future. Incorporation of additional orthogonal separation modes to perform n-dimensional separations will lead to yet further enhancement of peak capacity. Because there is no theoretical limit on the number or type of separations that can be coupled on-line, the increases in resolving power could be substantial. It is to be hoped that readers will respond enthusiastically to the solutions and ideas described in this issue, and be encouraged to develop multidimensional systems in new and exciting directions.
Marja-Liisa Riekkola is Professor of Analytical Chemistry at the University of Helsinki, Finland. Her research is focused on the development of instrumental analytical techniques (capillary electromigration and multidimensional chromatographic techniques, miniaturization, field flow fractionation, and on-line coupled techniques). Special emphasis has been put on theoretical, methodological and technical challenges. She is a member of the Editorial Advisory Board of six international journals. MarjaLiisa Riekkola has published over 200 scientific papers.
