Direct injection of aqueous samples in packed column supercritical fluid chromatography of isosorbide-5-mononitrate from drug release testing.

A method for the analysis of aqueous samples of isosorbide-5-mononitrate (5-ISMN) is presented. It is based on packed column supercritical fluid chromatography (SFC) using 20% of 2-propanol in carbon dioxide as the mobile phase and a diol silica column as the stationary phase. Using the described conditions it is possible to quantitate 5-ISMN released from Imdur tablets in gastric media. The precision upon repeated injections was 2% (RSD) at the 20 microg/ml level (n=8), using peak height measurements, when the solution was circulated through the sample loop of the injector. Samples from drug release testing that had been analyzed with reversed phase LC were analyzed with the present method and the results agreed well. It is also possible to monitor the drug released in a dissolution-testing vessel through direct on-line continuous loading (recirculation) of the sample loop of the SFC instrument.