Relationships for modeling the performance of rectangular gas chromatographic columns

Abstract

Golay's theory for open tubular GC columns was recently revised for application to rectangular GC columns. The HETP was found to be the same as for open tubular columns provided the average linear velocity, u, and the resistanceto-mass-transfer-in-the-gas-phase, C , are redefined. In this paper, a simplified M expression for the average linear velocity is derived and used to fit a variety of exit flow data collected on microfabricated rectangular GC columns. Also the resistance-to-mass-transfer-in-the-gas-phase is studied and the results compared to earlier relationships derived by Giddings, Chang, Myers, Davis and Caldwell, and by Golay. The three theories agree, with the present theory predicting a slightly higher value for C for large retention indices. The slightly higher value for C is M M attributed to the geometry for the rectangular column that is better modeled with the present theory than the former theories.

Computer simulation and theory of the diffusion- and flow-induced concentration dispersion in microfluidic devices and HPLC systems based on rectangular microchannels

“…(11) have been reported that rely on different approximations or boundary conditions [25][26][27][28][29][30][31][32][33]. It has been shown that additional contributions to HETP are generated at the side-walls of rectangular channels when these channels have a finite width [25][26][27][28][29][30][31][32][33].…”

“…Therefore, Eq. (11) holds for a rectangular channel of very large aspect ratio (parallel-plate or slab geometry: w h), and not for a square column (w = h) as suggested recently [26,33]. It should also be mentioned that Golay's theory does not apply to the domain of very high flow velocities since the derivation neglects any higher order terms [16].…”

“…Microfabricated devices usually incorporate channels that roughly have a rectangular cross-section. The performance of rectangular chromatographic columns has been analyzed first by Golay [16] (see also [21]), and was studied extensively in recent contributions [25][26][27][28][29][30][31][32][33]. In addition to theoretical treatments, numerical modeling of mass transfer has proved to be successful in tracing down the performance of such columns [33][34][35][36][37].…”

Design, fabrication and characterization of monolithic embedded parylene microchannels in silicon substrate

“…26,27 Low flow resistance resulting from the channel profile also facilitates high volumetric flow rate, which makes it possible that the channel length can be further increased without excessively increasing the injection pressure for maintaining reasonable fluidic flow rate and analysis time. 5 HAR channels are generally micromachined in a vertical paradigm to have a high density of channels per unit area on a chip and therefore provide a long vertically-accumulated absorption path length for optical detection.…”

On the two-domain equations for gas chromatography.

“…In recent years columns of rectangular, or nearly rectangular cross section have been used in micro-fabricated GC columns. Several authors have analyzed GC columns with rectangular cross sections [8,14,5,6,1,10]. However, all of these authors have assumed that the cross sections are uniformly coated with a thin layer of stationary phase.…”