Turbulent supercritical fluid chromatography in open tubular columns

Abstract

Portions of this section are copied from my publication. Michael Galietti, Valerie Peulon-Agasse, Pascal Cardinaël, Michael Fogwill, Sebastien Besner, Fabrice Gritti. Turbulent Supercritical Fluid Chromatography in Open-Tubular Columns for High-Throughput Separations. Analytical Chemistry, American Chemical Society, 2020, 92 (11), pp.7409-7412., with permission A novel chromatographic mode utilizing turbulent flow to perform ultra-fast separations and screen chiral compounds in supercritical fluid chromatography (SFC) is described. Carbon dioxide at high flow rates (up to 3.8 mL/min) is delivered into gas chromatography, open-tubular columns (OTCs) to establish turbulent flow at Reynolds numbers as high as 9000. Post column dispersion is eliminated by using a modified UV detector that takes measurements directly on column. Upon crossing the laminar-to-turbulent flow transition regime, a significant reduction in plate height is observed resulting in a 2.67x increase in peak capacity from the laminar regime. Reduced plate heights as low as 27.4 are observed in the turbulent regime, representing an 81% decrease from the laminar regime. This is explained by the massive reduction of the mass transfer resistance in the mobile phase due to flatter flow profile and faster analyte dispersion across the column diameter. Demonstrated in this work are separations of 2, 3, and 4 polyaromatic hydrocarbons: benz(a)anthracene - anthracene, phenanthrene - pyrene - triphenylene, and naphthalene - phenanthrene - pyrene - triphenylene, representing the first ever separations with this mode of chromatography. The 4-compound separation occurs in only 9 seconds over a 2.2 second separation window using a poly(dimethylsiloxane-co-methylphenylsiloxane) coated OTC, a speed seldomly achievable with the highest performance LC systems currently on market. Additionally, three chiral compounds and three chiral cyclodextrin-incorporated OTCs were evaluated at high temperatures (90-120°C) and high CO2 flow rates (3.3-3.7 mL/min) to demonstrate column stability and application of this method for rapid screening. Turbulent SFC provides a separation method for users desiring to achieve separation speeds above what is currently available with ultra-high pressure LC systems and do so without the efficiency loss commonly observed at maximum allowable speed.--Author's abstract