THE USE OF NITROUS-OXIDE FOR SUPERCRITICAL-FLUID EXTRACTION OF PHARMACEUTICAL COMPOUNDS FROM ANIMAL FEED

Supercritical fluid extraction (SFE) coupled ''off-line'' with HPLC an alysis has been applied to pharmaceutical analysis: two different matr ixes (rodent and dog feed) were spiked with compounds under investigat ion in pharmacological studies in order to study the supercritical ext raction of such matrixes prior to further analysis and quantification of the compounds of interest. The fluid flow-rate in the SFE system wa s governed by the geometric characteristics (internal diameter and len gth) of the linear fused silica capillaries. The changes in fluid flow -rate, between experiments, for each new restrictor, required the intr oduction of the term Total Gaseous Fluid Volume (TGFV), which enabled a series of extraction results to be compared. The comparative behavio r of nitrous oxide and carbon dioxide as supercritical extraction flui ds was investigated. Results obtained using pure supercritical fluids with high solvating power (density 0.79 g ml-1) and fluids modified wi th a polar liquid solvent (methanol and acetonitrile) are discussed.