The effects of changing the composition of a mixed mobile phase in electrochemically modulated liquid chromotography

The research presented in this thesis investigates the effect of the organic modifier, acetonitrile (ACN), as an additive to an aqueous mobile phase on the electrosorption of aromatic sulfonates onto porous graphitic carbon (PGC), as probed by electrochemically modulated liquid chromatography (EMLC). EMLC is a technique that employs a conductive material such as PGC as both the stationary phase and the working electrode. This dual functionality enables the manipulation of chromatographic retention by changing the potential applied to the stationary phase. This change alters the electrosorption process at the solid-liquid interfaces. Previous works have investigated these changes by applying the Gibbs adsorption equation to determine the interfacial excess (?), surface tension (d?), and surface charge (qM). This thesis incorporates the Gibbs adsorption equation to evaluate the effect ACN has on the electrosorption of aromatic sulfonates. This study is then followed up by using attenuated total reflection FTIR spectroscopy (ATR-FTIRS) to study the interactions in the mobile phase of this system, which consisted of mixed water:acetonitrile solutions with benzene as the solute and lithium perchlorate (LiClO4) as the supporting electrolyte.