SUPERCRITICAL-FLUID EXTRACTION RECOVERY STUDIES OF BUDESONIDE FROM BLOOD-PLASMA

In this article we have studied extraction recoveries of the corticosteroid budesonide from human blood plasma. The biological material was spiked with H-3-budesonide at a concentration of 93 nM. The analyte was extracted both as a pure substance and from the biological matrix. The performance of the packed column used for trapping the analytes was investigated. Special interest was focused on the performance of the trap using large concentrations of methanol in the extraction fluid. High trapping temperatures were needed for full recovery of the steroid. However, excessive temperatures were also shown to cause thermal degradation of the analyte. The extraction method sequence also had some impact on extraction recovery and repeatability. For example, some analyte loss occurred if depressurization was performed prior to trap rinsing. Reasonably high steroid recoveries, above 80%, could be obtained from the plasma samples. When pure CO2 was used, water in the matrix modified the extraction fluid, resulting in high analyte recovery. An alternative technique was to remove the water in a first low density step. The steroid was then extracted at conditions optimal for a dry matrix in a successive extraction.