Advanced Separation and Detection Methods for Supercritical Fluid Chromatography

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Our research is aimed at replacing organic solvents with environmentally cleaner alternatives, which is a growing concern in analytical chemistry. Many analytical laboratories coping with mounting hazardous waste and slow sample throughput are now switching to supercritical CO2 as a mobile phase, due to its low cost, relatively green nature, and remarkable properties. For instance, in supercritical fluid chromatography (SFC), it provides faster separations than liquid chromatography and allows heavier compounds to be analyzed than gas chromatography. However, supercritical carbon dioxide is non-polar and requires a polar organic modifier like methanol to be added for it to separate polar analytes. This removes the green benefits of SFC and destroys its otherwise unique ability to use the highly desirable universal flame ionization detector (FID). These limitations can seriously constrain SFC users, who frequently include the pharmaceutical, petroleum, and polymer industries, which are prevalent in Canada. We will develop a new separation method for SFC that was recently discovered in our laboratory. It is based on using water as a novel stationary phase and does not employ organic modifiers but only pure supercritical carbon dioxide. The method also analyzes polar molecules well and is FID compatible, making it potentially very useful. Our work will critically advance this approach and its capabilities, and allow it to analyze important classes of molecules that are currently problematic. For instance, we will attempt to alter the water stationary phase composition to allow it to separate chiral molecules, which are of tremendous importance to drug discovery. If possible, it will open a new avenue to customizing pharmaceutical separations. Through altering the pH of the water phase, efforts to separate ionizable analytes will also be made. This could allow a host of important analyses of organic acids and bases, which are of broad concern to pharmaceutical, petrochemical, and other industries. In a parallel approach, we will make an unconventional attempt to dynamically alter the water stationary phase pH during separations in order to manipulate analyte retention. If it works, it could allow for the ultimate control in separations, where analytes can be eluted on demand. Such an advance could have huge impact in the ability to analyze for target substances in large complex matrices, such as naphthenic acids in heavy oil. In other work, we will examine if sulfur species can also be analyzed and to what extent. If so, we will pair the water phase with a sulfur specific detector and create one of the most selective approaches to sulfur analysis available. A powerful new sulfur detector that we invented will also be examined in a related approach. These efforts will greatly simplify the analysis of sulfur compounds in complex samples like crude oil and will give a competitive edge to petrochemical users.