Supercritical fluid extraction as a sample preparation technique for the direct isolation of drugs from plasma prior to analysis.

Supercritical carbon dioxide was used for the direct extraction of drugs from plasma prior to analysis. The supercritical fluid was directly passed through plasma samples spiked with either a neutral (flavone) or an acidic (ketorolac) drug. The addition of an antifoam agent to the plasma prior to extraction was required to avoid restrictor plugging caused by denaturation of the plasma proteins by the supercritical fluid. The effluent from the extraction cell was bubbled through a small volume of methanol or into an empty tube to trap the extracted drug. The effect of extraction pressure and time on absolute recovery were examined. The absolute recovery, selectivity, precision and accuracy of the supercritical fluid extraction approach was compared to conventional liquid-liquid extraction using reversed-phase HPLC with ultraviolet detection.