Very Fast Gas Chromatography with a Ballistic Heating and Ultra fast Cooling of the Column

R. Kubinec¹*, Ž. Krkošová¹, H. Jurdáková¹, J. Blaško¹, I. Ostrovský¹, L. Soják¹, J. Ševčík²

^{1Chemical Institute, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, SK-845 45 Bratislava, Slovakia
^{2Department of Analytical Chemistry, Faculty of Natural Sciences, Charles University, Hlavova 2030, CZ-128 40 Prague, Czech Republic}

Abstract
An overview of the existing methods for minimization of the analysis time in gas chromatography (GC) is given and a new system for fast temperature programming and very fast cooling down is evaluated. In this study, a system of coaxial tubes, a heating/cooling module (HC–M), has been developed and studied, with a capillary column placed inside the HC–M module. The module itself is heated by the GC oven and cooled down by an external cooling medium. The HC–M module is heated up at rates of up to 330 °C min^-1 and cooled down at a rate of 6 000 °C min^-1. The GC system is prepared for the next run within a few seconds. The HC–M module permits good separation reproducibility, comparable with that of conventional GC, expressed in terms of the reproducibilities of the relative retention times and the peak areas of analytes. The HC-M module can be used within any commercial gas chromatograph.

Chromatographic characterization
. The potential of the system designed is demonstrated on a separation of a mixture containing twenty six n-alkanes in the range of n-C₁₀ to n-C₅₀, (Fig. 4). Separations of n/alkanes have been used to study the effect of the heating rate on the separation capability (criteria SN, n) and the analysis time. We have found that the separation number SN was in a range from 7.9 (for C10-C12) to 3.4 (for C48-C50), while the peak capacity was n = 107 and the speed of analysis was 25 SN min^-1.
Table 3 contains qualitative and quantitative results obtained with the HC-M system. The reproducibility of the peak retention times, obtained from six repeated measurements, was RSD = 0.25 % on average. The reproducibility of the peak area expressed in terms of RSD was in a range from 0.63 % for n-dodecane to 9.3% for n-pentacontane.
A separation of a phenol mixture on a short column with a very high heating rate is shown in Figs. 5 and 6. The total analysis time (including cooling) was 30 s on a 2.5 m column with the HC-M module. Eleven phenol compounds were analyzed within 0.4 min and all of them were resolved (Fig. 5). Fig. 6 shows 13 repeated GC separations within 6 minutes.}