Supercritical fluid chromatography and enhanced fluidity liquid chromatography : green alternatives to conventional liquid chromatography

The growing interest in high throughput assays is the result of the increasing numbers and because of the growing complexity of samples to be analyzed in pharmaceutical environments. The low viscosities and high diffusivities of sub- and supercritical fluids allow highly efficient separations to be achieved with significant analysis time gains, in comparison to High-performance liquid chromatography (HPLC). In addition at the start of this research in 2009 there was a global shortage of acetonitrile, a solvent which is widely used in the pharmaceutical industry for the analysis of drug substances and drug products. As a consequence, seeking to use alternative solvents or analytical methods to minimize the impact of this shortage and its environmental impact was and is a contemporary highly relevant concern. CO2 is particularly attractive as an alternative mobile phase because of its green character and as it is easily brought under supercritical conditions (which are reaches at 31°C and 73.8 bar). In chromatography liquid CO2 is therefore often used under sub- or supercritical as an extracting solvent and/or as the mobile phase with or without added organic modifier. In the framework of the Pfizer Analytical Research Centre (PARC) and a general revival of SFC mainly because of the release of new instrumentation, SFC was critically re-evaluated in this study for analysis of achiral and chiral pharmaceuticals. In the same framework, EFLC was evaluated as the same instrumentation is used. Important in this evaluation is that ruggedness or robustness is taken into considerations because this is a prerequisite for a technique to recognize a breakthrough in a regulated environment such as the pharmaceutical industry. Evaluation in the SFC- and EFLC-mode of the recent developments made in LC related to column formats (porous particles, core shell particles, smaller particles, etc.) is included in this study

Comparison of green enhanced fluidity reversed phase liquid chromatography with HPLC

The growing interest in high throughput assays is the result of the increasing numbers and complexity of samples being produced by modern combinatorial synthetic procedures. The low viscosities and high diffusivities of enhanced fluid mixtures allow highly efficient separations to be achieved with analysis time gain as compared to High-performance liquid chromatography (HPLC). In this study, possibilities and limitations of HPLC mobile phases ethanol/water, acetonitrile/water, and methanol/water at higher proportion aqueous content and acetone/ acetonitrile as non-aqueous mobile phases were evaluated to compare liquid chromatography with green enhanced fluidity liquid chromatography (EFLC) separations by adding different concentrations of carbon dioxide as ternary mobile phase. The techniques were evaluated via van Deemter plots on reversed phase columns. EFLC allows reduce analysis time reduction and to obtain improved column efficiencies by effectively increasing the permeability of the system and by ensuing faster diffusion kinetics and further better selectivity. Similarly the impact on retention and separation in reversed phase using C18 and Naphtylethyl (Pi NAP) stationary phases were explored. A mixture of 16 priority PAH pollutants were used to investigate these effects. Next to interesting changes in selectivity improvements in analysis time and shifting Van Deemter curves could be measured in this way demonstrating the potential of this new green variant of HPLC