Modeling the competitive adsorption of sample solvent and solute in supercritical fluid chromatography

Effect of the injection of water-containing diluents on band broadening in analytical supercritical fluid chromatography

“…The injection of pure MtBE and pure ACN conducted to a single large negative perturbation peak around 0.6 min, while the injection of pure MeOH led to a right angled-triangular perturbation peak, suggesting that MeOH molecules are adsorbed on the stationary phase (Figure 2a). This MeOH adsorption on SFC stationary phases has already been evidenced [22]. The injection of pure ACN provided the exact same elution profile as the injection of MtBE, suggesting that ACN is not retained on the stationary phase.…”

“…Several SFC studies demonstrated that common polar solvents can exhibit retention on polar stationary phases [21,22]. Detecting at 200 nm so that the MeOH co-solvent exhibited a significant absorbance, it was possible to follow the system peaks due to the elution of solvent molecules.…”

Opportunities and challenges of liquid chromatography coupled to supercritical fluid chromatography

“…In addition to differences between sample diluent and mobile phase, injection effects can also be engendered by the adsorption of the diluent itself onto the stationary phase. Several SFC studies revealed that the most commonly used sample diluents, such as methanol or acetonitrile, showed a significant retention on various types of stationary phases [50,[57][58][59]. This behaviour can lead to a competition between the analyte and the diluent to access the stationary phase, which in turn, can result in unusual peak shapes.…”

“…More precisely, its impact was found to be dependent on the relative retention of the analyte compared to the diluent. Using an alkylamide column and neat CO2 as mobile phase, Redei et al [59] compared the chromatograms of a series of n-alkylbenzenes dissolved in a retained (methanol) and in a non-retained diluent (heptane) (Figure 4a). The retention of methanol can be visualized at 200 nm (red circle).…”

High-Throughput and Ultrafast Liquid Chromatography

“…i.d.) is often used to reduce the effects of extra-column band broadening in LC, it can promote the onset of turbulent flow and increases in backpressure when used with high-flow SFC. − It should be noted, though, that recent results indicate that utilizing turbulent flow conditions may also have the potential for increasing resolution with high-throughput SFC separations of less retained compounds. − Other key factors in avoiding significant peak distortion for ultrafast SFC methods include selecting appropriate sample diluent − and organic modifiers − as well as properly maintaining column temperature control. ,− When suitable conditions are obtained, separations in the 1–10 s range are achievable for moderately complex mixtures using SFC (Figure ). …”