Studies of peroxyoxalate chemiluminescence: Use of electrogeneration and use of a novel reaction medium, supercritical carbon dioxide

Peroxyoxalate chemiluminescence is a commonly used detection method for liquid chromatography. The low detection limits and wide dynamic range that this reaction offers for the analysis of easily oxidizable fluorophores account for the popularity of this detection method.Peroxyoxalate chemiluminescence detection in high-performance liquid chromatography suffers from the need for two post-column reagent additions. The first half of this research evaluated the use of electrogeneration of the peroxyoxalate chemiluminescence reaction as a means of reducing or eliminating these post-column reagent additions. In acetonitrile, peroxyoxalate chemiluminescence can be electrogenerated at potentials between $-$1.5 and $-$1.9 V (versus silver/silver chloride). Imidazole, a catalyst for peroxyoxalate chemiluminescence, was found to interfere with the electrochemistry of the model peroxyoxalate and thus the emission of light with electrogenerated peroxyoxalate chemiluminescence. Conversely, electrogenerated peroxyoxalate chemiluminescence is enhanced in the presence of hydrogen peroxide, a necessary reagent for solution-initiation of this reaction; this enhancement is time dependent. Direct comparison showed electrogenerated peroxyoxalate chemiluminescence to be less sensitive than solution-initiated peroxyoxalate chemiluminescence.The behavior of supercritical fluids is becoming more fully understood. This understanding, coupled with the environmental benefits of working with some of these fluids, has led to an almost explosive growth in the use of these fluids in industrial processes and analytical chemistry. No solution-phase chemiluminescent reaction has previously been carried out in a supercritical fluid. This research sought to evaluate the effect that this novel reaction medium, liquid and supercritical carbon dioxide, would have on the behavior of the peroxyoxalate chemiluminescent reaction.The behavior of the peroxyoxalate chemiluminescent reaction was unchanged by the change in reaction medium from organic solvents to liquid and supercritical carbon dioxide, with the exception that reaction kinetics were faster. Increasing the reaction temperature led to an increase in chemiluminescent intensity; increasing pressure did not significantly affect chemiluminescent intensity.Preliminary experiments were conducted to evaluate the analytical utility of the peroxyoxalate chemiluminescent reaction carried out in liquid and supercritical carbon dioxide. In a flow injection analysis application, the detection limit for 9,10-diphenylanthracene is 1 nM. Also, this detection method was demonstrated to be compatible with the use of several organic solvents that are commonly used as modifiers with supercritical carbon dioxide. Experiments showed that the peroxyoxalate chemiluminescent reaction could be used for the detection of fluorophores separated by supercritical fluid chromatography; the detection limit for 9,10-diphenylanthracene was 1.2 $\mu$M.U of I OnlyETDs are only available to UIUC Users without author permissio