Separation of oligomers by supercritical fluid chromatography

Supercritical fluid chromatography (SFC) is a powerful technique for the pr eparation of uniform oligomers, which have no molecular weight distribution . However, the separated sample at one fractionation is often only a small quantity, and the optimization of experimental parameters is necessary for efficient collection. In this study, we measured the increase or decrease o f the peak resolution and the analysis time for the SFC of polystyrene olig omers and polyethylene glycol oligomers by varying four experimental parame ters, i.e. initial temperature of column, temperature gradient, modifier fl ow-rate, and modifier gradient. To maximize the separation efficiency, we a pplied a chromatographic response function (CRF) to the obtained experiment al data as a function of the desired peak separation, the maximum acceptabl e analysis time, and an arbitrary weighting factor between them. The weight ing factor was adjusted to achieve the desired balance between peak separat ion and analysis time. Numerical values of CRF fluctuated with the chromato graphic performance and presented an optimum condition for a given set of t he three parameters.