ABSTRACT
Critical-mixture curves for 13 CO2-solvent binary mixtures were estimated using the peak-shape method. Mixture critical points were determined within 1 degrees C and 1 atm. The results for CO2-toluene and CO2-methanol were compared to previously reported data from high-pressure view cell studies. No more than a 3% difference was observed in the data generated by the two different techniques. A few abnormalities encountered while using the peak-shape method are also discussed.
Subject(s)
Carbon Dioxide/chemistry , Methanol/chemistry , Toluene/chemistry , PressureABSTRACT
Since flow injection (FI) is a dilution technique, efforts have been undertaken to minimize online dilution or dispersion. Solutes in supercritical fluids exhibit increased diffusion coefficients which have been shown to decrease dispersion of the sample zone. This work investigates the use of supercritical fluids (or CO(2) modified fluids) as carrier streams for FI. Both a non-reacting tracer and an online chemical reaction were employed to investigate the behavior of solutes in supercritical and near critical systems. Further, these results are compared to those obtained in the system studied with a conventional carrier stream. Plots of peak response vs% CO(2) modifier increase with a sharp break at moderate modifier composition (20-30%). Plots of peak variance vs% CO(2) modifier show decreased variance with increasing % modifier. The system was also optimized with regards to temperature and pressure. The optimized system displayed improved limits of detection and decreased variance relative to 0% CO(2) modifier carrier streams.
