Determination of iloprost in 5% dextrose in water solution by reversed-phase high performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method utilizing absorbance detection was developed for the rapid and precise determination of the stable prostacyclin analogue iloprost in 5% dextrose in water solution (D5W). Samples were prepared for chromatographic analysis by extracting the drug into chloroform, evaporating the solvent, and solubilizing the residue in methanol. The resulting solutions were chromatographed on a Shandon ODS Hypersil column using 0.02 M potassium phosphate (pH 3.0), methanol, and acetonitrile (456:144:400, v/v) at a flow rate of 1.8 mL/min. 2-Naphthoic acid was employed as an internal standard. The detector response at 207 nm was linear (correlation coefficient greater than 0.9998) for concentrations of iloprost from 10 ng on-column, the lower limit of quantitation, up to 7 micrograms on-column. The precision of the method was approximately 5% based on peak area, with a recovery of iloprost from D5W of 87%. Liquid-liquid extraction was found to be superior to solid-phase sorbent extraction as a sample preparation method due to incompatibility of dextrose with the sorbent bed.