FUNDAMENTALS OF RETENTION AND MASS FLOW IN SUPERCRITICAL FLUID CHROMATOGRAPHY

Abstract

The aim of the dissertation is to delve into the fundamentals of SFC, more specifically topics related to uncommon retention behavior observed in the case of neat carbon dioxide mobile phases, then the challenges of accurate mass flow rate measurements and lastly, exploring the options and limitations of hold-up time measurements. Our research objectives are described in detail as follows: 1. Studying the uncommon retention behavior of n-alkylbenzene homologues and the effect of different sample solvents on chromatographic efficiency: a) screening of different stationary phases and sample solvents (acetonitrile, heptane and methanol) to find anomalous retention behavior; b) determination of the single-component adsorption isotherms using the bi-Langmuir model and the inverse method (IM); c) determination of the competitive bi-Langmuir adsorption isotherms to understand the competition of the sample solvents and solutes; d) construction of a numerical model in order to simulate the competitive adsorption in the case of the real and two hypothetical compounds. 2. Scouting the effects of placement, experimental conditions and injections on mass flow measurements: a) studying the effect of placing the Coriolis flow meter (CFM) and pressure gauge at different positions in the SFC system; b) studying the effect of pressure and temperature on mass flow rate; c) studying the effect of injections on the mass flow rate at equilibrium.

3. Exploring the limitations of hold-up time measurements including the study of nitrous oxide as a new unretained marker: a) comparison of different compounds previously used as unretained markers in SFC; b) studying the effect of the amount of organic modifier in the mobile phase; c) surveying whether the stationary phase has any effect on the detection of hold-up time markers.