Packed-column supercritical fluid chromatography of a new dihydropyridine drug based on direct injection of emulsion samples

In this paper, a method based on direct injection in packed-column supercritical fluid chromatography (SFC) for the determination of a dihydropyridine drug in emulsion samples is described. To optimize the chromatographic system, an experimental design approach with four factors was applied. The parameters studied were modifier-carbon dioxide ratio, flow-rate, column temperature and back-pressure. A face-centred central composite design (CCF) yielded a model with good fit and high predictive power. Using plates per second as the response parameter, a fast method for quantitative determination of the analyte was developed. Within the experimental space investigated, the concentration of the polar component in the mobile phase and the flow-rate were found to be the important parameters. Peak compression effects, resulting in high apparent peak numbers (>80 000 versus a nominal value of 7000) were encountered when emulsion samples were injected.