GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

Abstract

GC column selectivity can be continuously adapted to suit analytical needs using a flow-tuneable tandem system. Its application for the separation of complex mixtures requires a deep understanding of the theory in this area. Although a number of researchers have developed specific models, a general and exhaustive theory is still missing. In this paper, we have made an implementation of pre-existing models on tandem-column assemblies operated isothermally. In particular, we have investigated the effect of column length and diameter, phase thickness, and oven temperature on chromatographic parameters, such as capacity factor, selectivity, and intrinsic resolution. A new approach for the correct choice of the working temperature has been proposed.

GC models for separation optimization in pressure‐tunable tandem capillary columns operated isothermally

“…Equation numbering, mathematical symbols and acronyms employed below are those defined in Ref. . New equations introduced in this work are numbered in consecutive order with the last equation derived in Ref.…”

“…New equations introduced in this work are numbered in consecutive order with the last equation derived in Ref. . A synoptic list of the symbols and equations cited or introduced in this article is provided in Supporting Information Tables S1 and S2.…”

“…Therefore, before carrying out control experiments to check the mathematical model proposed in Ref. , it was necessary to develop a new interface to guarantee the quick and correct positioning of the two capillary columns at the connection point. This device has been designed by taking into account the following objectives: The column interfacing shall occur within a cylindrical glass insert (liner) properly deactivated. The gas introduction and/or removal (splitting) at the column junction shall be carried out in a direction tangential to the two GC columns using inert capillaries placed inside the liner in close proximity to the junction. At the junction point the liner shall have a restriction whose minimum width shall be less than or equal to the internal diameter of each GC column to be connected through the interface. The coupling area shall be visible in order to facilitate the correct alignment of the two GC columns and the two inert capillaries. The hydraulic seals shall be placed outside of the liner so as to be sufficiently distant from the gas flow area. …”

“…In particular, pressure tuning at the serial connection of two chromatographic columns has provided the most elegant and versatile solution. A comprehensive description of these methods was given in the first part of this report on our research in which we improved the mathematical model on multichromatographic systems that operate in the isothermal mode by describing, inter alia, an original approach to select the optimal column temperature.…”

“…In the third part of our study, which will be published in the near future, the mathematical approach described in Ref. will be applied to the prediction of the operating temperatures that enable the achievement of the best possible chromatographic resolution of test solutions containing linear and branched hydrocarbons, halogenated organics, and organic solvents.…”