Chip-Based Multicapillary Column with Maximal Interconnectivity to Combine Maximum Efficiency and Maximum Loadability

Abstract

On the basis of our previous work on the design of pillar array columns for liquid chromatography, we report on a new pillar array design for high-efficiency, high volumetric loadability gas chromatography columns. The proposed pillar array configuration leads to a column design which can either be considered as a packed bed with perfectly ordered and uniform flow paths or as multicapillary columns (8 parallel tracks) with a maximal interconnectivity between the flow paths to avoid the so-called polydispersity effect (dispersion arising from the inevitable differences in migration velocity between parallel flow paths). Despite our relative inexperience with column coating, and most probably (not supported by data) suffering from the same problem of stationary phase pooling in the right-angled corners of the flow-through channels as other chip-based GC devices, the efficiencies obtained in a L = 70 cm long and 75 μm deep and 6.195 mm wide chip for, respectively, quasi-unretained and retained components (k = 7) went up to N = 60 000 and 12 500 under isothermal conditions using H as carrier gas and a downstream restriction. Under programmed temperature conditions (T = 80 °C, T = 175 °C at 30 °C/min, and a H flow of 0.4 mL/min), a peak capacity of 170 was obtained in 3.6 min. For retained compounds, the optimal flow rate is found to be on the order of 0.4 mL/min, achieved at an operating pressure of 2.3 bar. Intrinsically, the column combines the efficiency of a 75 μm capillary with the volumetric loadability of a 240 μm capillary.

Effect of diffusional bridging in multicapillary packing

“…New ordered packings like micropillar arrays [12,16] have been found efficient but lack in several respects the benefits of radial diffusional dampening, and are subject to wall effects. Micropillar arrays are today limited in resolution to micrometric structures [12] and need specific, microflow equipment.…”

“…The Table 2 below reports the values of theoretical plates heights computed by (16) and (17) in the simplest case of virtual channels with separating walls having negligible mass transfer resistance and no retention characteristics.…”

“…The main observation is that the loss in efficiency induced by the channels' diameters dispersion is limited to moderate fractions of the total height for relative square deviation (RSD) lower than 5%. Table 3 reports the results of our simulation tools and the corresponding partial height of dispersion computed according to (16) and (17) with α disp = 1 in different conditions, namely by varying: For the same column length of 1 mm. The relation between theoretical and simulated data is linear with a correlation coefficient R 2 of 0.9976.…”

“…Schisla et al [13], Sidelnikov [14,15] and Jespers [16] analysed the behaviour of a bunch of individual capillaries.…”

Micro Gas Chromatography: An Overview of Critical Components and Their Integration

“…50,57,58,101−103 Very recently, the Desmet group designed efficient separation columns by using radially elongated pillars (REPs) as shown in Figure 5. 48 REPs are elongated perpendicular to the direction of flow and they provide a longer path for the gas to travel mimicking the increased length of columns, thereby achieving a high number of plates. While majority of the reported studies have used wall-coated (or walland pillar-coated) open-tubular microcolumns, relatively few studies have described the packing of stationary phase particles inside the channels of microcolumns (Figure 4c,d).…”