RESUMO
An extremely rapid tool for continuous flow synthetic process optimisation is described. A microfluidic reaction system operating in continuous flow is used in conjunction with confocal Raman microscopy to afford rapid molecule synthesis and product quantitation. Accordingly, the approach allows for rapid reaction optimisation within a continuous flow system. Specifically, the catalytic oxidation of isopropyl alcohol (IPA) to acetone using tetra-N-propylammonium perruthanate (TPAP)/N-methylmorpholine N-oxide (NMO) in a radial interdigitated micromixer is studied as a model reaction system. The composition of the reaction effluent can be determined with great facility and information relating to catalyst/co-oxidant ratios, catalyst turnovers and reaction endpoints extracted. Specifically, variation of catalyst and co-oxidant volumetric flow rates between 0 and 50 microL min(-1) is used to vary reactant concentrations, define reaction residence times and control product conversions between 0 and 100%. The rapid nature of the system allows chemical information to be gathered and utilised on a sub-minute timescale.
RESUMO
This paper describes the use of reversed-phase, reversed-polarity head-column field-amplified sample stacking (HCFASS) for on-line sample concentration in conventional capillary electrophoresis. The effective stacking efficiency was determined as a function of sodium hydroxide concentration in the sample matrix. Results concur with theoretical predictions where stacking efficiency depends on the conductivity (electric field strength) and electrophoretic mobility in the sample matrix solution. Fluorescein isothiocyanate-derivatized aniline and 2,4-dimethylaniline were dissolved in sodium hydroxide (800 microM), separated in a phosphate running buffer (0.05 M, pH 9.0) and detected utilising laser-induced fluorescence. The use of reversed-phase, reversed-polarity HCFASS with laser-induced fluorescence detection yielded sensitivity improvements with respect to normal injection schemes in excess of three orders of magnitude, and a limit of detection as low as 10(-13) M.
