Kinetic behaviour in supercritical fluid chromatography with modified mobile phase for 5μm particle size and varied flow rates

Understanding and diminishing the extra-column band broadening effects in supercritical fluid chromatography

“…Among several approaches, using a low-viscosity fluid, such as fluidic CO 2 , results in very high diffusion coefficients and thus allows the use of higher flow rates without significant efficiency loss [1]. As a result, very fast and efficient separations can be performed in supercritical fluid chromatography (SFC) [2][3][4][5][6][7]. For example, a plate count of 182,000 plates can be achieved for a void time of 5.8 min * Corresponding author.…”

Occurrence of turbulent flow conditions in supercritical fluid chromatography

“…Taking the same example as before (F = 5 ml/min, d tub = 120 m), but now for neat supercritical CO 2 ( = 0.07 cP, = 800 kg/m), a Re number of a little more than 10,000 is found, showing that turbulent conditions can be expected from flow rates as low as 1.2 ml/min (Re equal to 2400) and certainly for flow rates above 2 ml/min. Optimal flow rates in SFC for 4.6 mm ID columns and 5 m are typically around 3-5 ml/min and for 2.1 and 3 mm columns packed with 1.8 m particles these can be expected to be in the range of 1-3 ml/min [1,[5][6][7]. For supercritical fluids, where the flow rate (F (ml/min)) and thus the velocity increases with decreasing pressure along the column, it is easier to express Re as a function of the mass flow rate (ṁ (g/s)).…”

Maximizing kinetic performance in supercritical fluid chromatography using state-of-the-art instruments

“…Due to the compressibility of the SFC mobile phase, its density and linear velocity varied along the column. Therefore, the average density increased with linear velocity when the outlet pressure was held constant (back pressure regulation, BPR) [26]. Because of these complex behaviours, the approaches used in HPLC to evaluate kinetic efficiency cannot be easily extrapolated to SFC conditions.…”

“…Because of these complex behaviours, the approaches used in HPLC to evaluate kinetic efficiency cannot be easily extrapolated to SFC conditions. Currently, three different methodologies are applied for evaluating the kinetic performance of SFC separations: (1) conventional method: changing the flow rate and column inlet pressure with fixed column length at constant outlet pressure, yielding changes in density [26][27][28], (2) isopycnic method: changing the flow rate at a given column length and keeping the average pressure (and thus average density) constant by adjusting the outlet pressure [29] and (3) variable column length method: changing the flow rate and column length by keeping the same inlet and outlet pressure (and thus the average density constant) [24].…”