Selectivity tuning of serially connected open-tubular (capillary) columns in gas chromatography. Part I: Fundamental relationships

Summary The evolution of the use of mixed phases or serial column combinations is outlined, leading to systems with fixed-length columns to be used in selectivity tuning (“multi-chromatography”). The difference between multi-chromatography and multi-dimensional gas chromatography is outlined. After discussing the system used in subsequent work, the fundamental relationships of multi-chromatography are detailed. Among the basic relationships the additivity of retention data, the relationship between the individual and composite capacity factors and the relative retentivity serving as the fundamental parameter of a multi-chromatography system are discussed. The relative retentivity is derived as a function of gas holdup times, pressures, and average velocities or flow rates. Finally, the relationships between individual vs. composite relative retention, efficiency, and resolution values are deduced. We dedicate this paper to the memory of our dear friend, Dr. S. R. Lipsky. Consolidated and enlarged text of part of the papers presented at the 37th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Atlantic City, NJ, March 10–14, 1986) (92–94), and at the Seventh International Symposium on Capillary Chromatography (Gifu, Japan, May 11–14, 1986) [95]. Part II will follow in the December issue.