Polarity change in capillary GC by serial‐column temperature optimization (SECAT mode in capillary GC)

Abstract

Key Words:Gas chromatography Capillary, glass SECAT-technique = stepless fine tuning of capillary Exponential influence of temperature on selectivity over a SECAT-technique ready for automation of column adjustment Instrumental and methodological details for primitive self selectivity by serial column temperature optimization wide range found on sample composition polarity made solution given Summary GC, including capillary GC, is rather inflexible, if a certain column length and stationary phase has been fixed for a given analytical problem. If the sample composition changes, one often has to change the column length and/or stationary phase, at least when something like optimum analytical conditions are needed. Temperature changes (or heating rates) can change the selectivity of a given column only within very limited ranges, due to the exponential effect of temperature on retention time. By serial coupling two chemically different capillaries, each run at another temperature, even the slightest changes of these two temperature values have a dramatic effect on the selectivity of the system for polar substances. We call this technique the SECAT mode of GC. Results are reported as retention index shifts, dependent on SECAT temperature data. This technique can in future easily be automated, thus enabling the analyst, for polar sample analysis, to adjust a given chromatographic system to his specific sample composition without touching the instrument.

Two-Dimensional Gas Chromatography. Concepts, Instrumentation, and Applications - Part 1: Fundamentals, Conventional Two-Dimensional Gas Chromatography, Selected Applications

“…EPA method 624 is an example. Stationary phase selectivity can also be continually optimized by coupling two columns in series and adjusting the relative temperatures [17], or pressure/flow rates in each segment [18,19]. This straightforward approach, pioneered by Deans [20] is amenable to treatment by computer simulation [21].…”

Aspects of High-Resolution Gas Chromatography as Applied to the Analysis of Hydrocarbon Fuels and Other Complex Organic Mixtures. Volume 1

“…The extra-column effects in MDGC have been assessed [227], and the effects of pressure and temperature upon solute behavior in coupled column systems have been investigated [228,229], Several studies have been presented which used coupled two-column MDGC systems [230][231][232]. Also, a theoretical investigation was presented [233] which examined the effects of polarity change in a capillary MDGC system. A paper recently presented discussed some of the requirements to convert a conventional gas Chromatographie system to a MDGC system [234].…”

“…Work has also been conducted with MDGC systems which incorporate the use of intermediate trapping [235] and a two-dimensional capillary system which did not use intermediate trapping [236]. Some very interesting recent work [237,233] has involved MDGC systems which emphasize the use of two separate ovens with different temperature versus time histories for obtaining Chromatographie separations. Practically every MDGC system of the second class will use the technique known as "heart cutting" for selectively capturing and then reinserting a certain fraction of a complex sample.…”

Multidimensional High-Resolution Gas Chromatographic Investigations of Hydrocarbon Fuels and Various Turbine Engine Fuel Precursors.

“…The use of highly selective stationary phases for the disengagement of troublesome compounds has recently been examined (20,211, and some MDGC work has been conducted where one of the ~ j stationary phases was of the liquid crystal variety. Such column systems should produce dramatic changes in chromatographic retention behavior by simply changing the temperature versus time profile.…”