Comprehensive two-dimensional gas chromatographic separations with a temperature programmed microfabricated thermal modulator

Abstract

Comprehensive two-dimensional gas chromatography (GC×GC) with a temperature-programmed microfabricated thermal modulator (μTM) is demonstrated. The 0.78 cm(2), 2-stage μTM chip with integrated heaters and a PDMS coated microchannel was placed in thermal contact with a solid-state thermoelectric cooler and mounted on top of a bench scale GC. It was fluidically coupled through heated interconnects to an upstream first-dimension ((1)D) PDMS-coated capillary column and a downstream uncoated capillary or second-dimension ((2)D) PEG-coated capillary. A mixture of n-alkanes C6-C10 was separated isothermally and the full-width-at-half-maximum (fwhm) values of the modulated peaks were assessed as a function of the computer-controlled minimum and maximum stage temperatures of μTM, Tmin and Tmax, respectively. With Tmin and Tmax fixed at -25 and 100°C, respectively, modulated peaks of C6 and C7 had fwhm values<53 ms while the modulated peaks of C10 had a fwhm value of 1.3s, due to inefficient re-mobilization. With Tmin and Tmax fixed at 0 and 210°C, respectively, the fwhm value for the modulated C10 peaks decreased to 67 ms, but C6 and C7 exhibited massive breakthrough. By programming Tmin from -25 to 0°C and Tmax from 100 to 220°C, the C6 and C7 peaks had fwhm values≤50 ms, and the fwhm for C10 peaks remained<95 ms. Using the latter conditions for the GC×GC separation of a sample of unleaded gasoline yielded resolution similar to that reported with a commercial thermal modulator. Replacing the PDMS phase in the μTM with a trigonal-tricationic room temperature ionic liquid eliminated the bleed observed with the PDMS, but also reduced the capacity for several test compounds. Regardless, the demonstrated capability to independently temperature program this low resource μTM enhances its versatility and its promise for use in bench-scale GC×GC systems.

Advancements in Microfabricated Gas Sensors and Microanalytical Tools for the Sensitive and Selective Detection of Odors

“…Thus, the optimum length, width, and height are generally a trade-off between achieving high efficiencies and reaching acceptable response and recovery times. In recent years, comprehensive two-dimensional microgas chromatography (2D-µGC) has been actively proposed in the literature to improve the separation capacity and performance of standard µGC devices [ 240 ]. Moreover, 2D-µGC is a new microanalytical technique that couples a first-dimension column (D 1 ) to a relatively short second-dimension column (D 2 ), whose retention properties help to increase the number of compounds separated at a given analysis [ 241 ].…”

Comprehensive two-dimensional gas chromatography: A perspective on processes of modulation

“…Going back to the modulation process, over recent years novel PRM devices have been described [23][24][25]. For example, in 2011 Panić et al proposed a simple transfer device based on the use of a 15-cm (× 0.28 mm ID) segment of stainless steel tubing, with a thick film of stationary phase (1 or 3 μm of polydimethylsiloxane -PDMS), looped outside the top of the GC oven [23].…”

“…In 2016, Collin et al reported the use of a temperature-programmed PRM system [25]: the entrapment and re-injection temperature ranges were from -25°C to 0°C and from 100°C to 220°C, respectively. A scheme of the PRM GC×GC-FID instrument is shown in Figure 2.…”

“…Therefore, a technological route focused on the evolution of the original model proposed by Phillips and coworkers [5,13]. In particular, the inclusion of a form of refrigeration (e.g., thermoelectric cooling), to efficiently-modulate highly volatile compounds (C5-C10 analytes), would be one of the main necessary modifications [23][24][25]. Though such a modification increases the complexity of both the modulator structure and its operation, it is also accompanied by a fundamental improvement in modulation performance.…”

Compact prototype microfabricated gas chromatographic analyzer for autonomous determinations of VOC mixtures at typical workplace concentrations

“…Members of our group have reported on a number of μGC and μGC × μGC components and systems in recent years [37][38][39][40][41][42][43][44][45][46][47][48][49][50] . We have also developed automated prototype instruments containing μGC systems for measuring low-to sub-ppb concentrations of trichloroethylene (TCE) in vapor-intrusion impacted homes 51,52 , and markers of explosives for transportation security 53,54 .…”