COMBINED SUPERCRITICAL FLUID EXTRACTION SOLID-PHASE EXTRACTION WITH OCTADECYLSILANE CARTRIDGES AS A SAMPLE PREPARATION TECHNIQUE FOR THE ULTRATRACE ANALYSIS OF A DRUG METABOLITE IN PLASMA

Supercritical fluid extraction was coupled with solid-phase extraction using octadecyisilane cartridges for the selective isolation of ultra trace levels of a drug metabolite, mebeverine alcohol, from plasma. Pl asma was directly applied to the extraction cartridge, the cartridge w as washed to remove protein and then extracted under supercritical con ditions using CO2/5% methanol. The effluent from the extraction cell w as bubbled through a small volume of 2-propanol to trap the extracted mebeverine alcohol. The effects of extraction pressure and temperature on analyte recovery were examined. The absolute recovery, selectivity , precision, and accuracy of the combined supercritical fluid extracti on/solidphase extraction approach were compared to those of convention al solid-phase extraction using gas chromatography/mass spectrometry i n the selected-ion monitoring mode. Mebeverine alcohol was used as a m odel compound, and dog plasma was employed as the biological matrix fo r these studies.