The use of porous graphitic carbon in liquid chromatography performance and polar retention effect

This thesis is primarily concerned with the use and development of Porous Graphitic Carbon (PGC) for High Performance Liquid Chromatography (HPLC). Chromatographic studies carried out using PGC since its introduction in 1988 have shown it to posses quite unique separating properties. In particular the media has been shown to be very selective for the separation of closely related compounds such as geometric and diastereoisomers. It has also been shown to be very retentive towards compounds of increasing polarity. The magnitude of this interaction is considerable, we define it as the retention over and above that which might have been predicted if the polar functional group was replaced with a non polar group of similar size. We have called this effect, the Polar Retention Effect on Graphite (PREG). Previous attempts to correlate retention on graphite with energies associated with those molecular interactions associated with other chromatographic media have been largely unsuccessful. This has in part been due to the fact that there has been no attempt to measure in units of energy the magnitude ofPREG. The main body of the thesis is then concerned with experiments, which provide information regarding the magnitude ofPREG. We investigate a) the relative strength of analyte/graphite interactions to that of analyte/solvent interactions, b) the effect of coating discrete or polymeric molecules to the graphite surface on PREG and c) measure the energy associated with PREG for a range of analytes and correlate this energy with physical and calculated parameters associated with each analyte. In order to gain a measure of PREG we have developed a method which allows PREG to be measured and quantified. Based on our values ofPREG we have put forward a hypothesis for the mechanism responsible for this interaction. Further work still needs to be done to strengthen this hypothesis, we therefore put forward a number of ideas and suggestions for future workers to which continue to investigate the mechanism associated with PREG