Peak Capacity in Two-Dimensional Liquid Chromatography

Department of Chemistry and Biochemistry, Southern Illinois University at Carbondale, Carbondale, IL 62901 1409, USA 

A minor problem with 2D peak capacity is that it is based on a square or rectangular tessellation (Guiochon et al., 1982) instead of a cubic closest packed 

Multidimensional Liquid Chromatography Theory and Applications in Industrial Chemistry and the Life Sciences, Edited by Steven A. Cohen and Mark R. Schure. 

This chapter examines another measure of the space used by 2D separations subject to correlation. Some researchers use the words, peak capacity, to express the maximum number of zones separable under specific experimental conditions, regardless of what fraction of the space is used. By definition, however, the peak capacity is the maximum number of separable zones in the entire space. No substantive reason exists to change this definition. The ability to use the space, however, depends on correlation. In deference to previous researchers (Liu et al., 1995 Gilar et al., 2005b), the author adopts the term, practical peak capacity, to describe the used space. The practical peak capacity is the peak capacity, when the separation mechanisms are orthogonal, but is less than the peak capacity when they are not. The subsequent discussion is based on practical peak capacity. 

Any measure of the coordinate correlation is arbitrary. Here, the linear correlation coefficient r is used, largely because it is familiar. It measures the quality of a least-squares fit of a line to coordinates, with a magnitude that varies from 0 (for uncorrelated random coordinates) to 1 (for fully correlated coordinates lying on the line). For the correlated coordinates in Fig. 3.1 b, d, and f, theoretical relationships for r, that is, r =/(p1 p2) can be derived as shown in Appendix 3B. They show that r lies between the inclusive bounds of 1/2 and 1 for WEG, and between the inclusive bounds, 0 and 1, for FAN and PAR. 

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Jandera, P., Novotna, K., Kolarova, L., Fischer, J. (2004). Phase system selectivity and peak capacity in liquid column chromatography—the impact on two-dimensional separations. Chromatographia 60, S27. 

Gilar, M., Daly, A.E., Kele, M., Neue, U.D., Gebler, J.C. (2004). Implications of column peak capacity on the separation of complex peptide mixtures in single- and two-dimensional high-performance liquid chromatography. J. Chromatogr. A 1061, 183-192. 

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