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 sup ercritical fluid chromatography (SFC) for the determination of a dihyd ropyridine drug in emulsion samples is described. To optimize the chro matographic 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 cent ral composite design (CCF) yielded a model with good fit and high pred ictive power. Using plates per second as the response parameter, a fas t method for quantitative determination of the analyte was developed. Within the experimental space investigated, the concentration of the p olar 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 en countered when emulsion samples were injected.