INVERSE ANALYTICAL SUPERCRITICAL-FLUID EXTRACTION OF ZOVIRAX-OINTMENT-5-PERCENT

Inverse supercritical fluid extraction (SFE) is a new approach to samp le preparation. In most cases SFE is used to remove the analyte from t he matrix, but in our investigation the analyte was retained in the ex traction vessel while the matrix is extracted. Our study investigates the isolation of acyclovir from the pharmaceutical agent Zovirax Ointm ent 5%. Acyclovir is a polar analyte and is insoluble in 2% methanol-m odified CO2, while the ointment carrier is very soluble in this fluid. A 100 mg sample of ointment can be extracted in 20 minutes with the a forementioned supercritical fluid. A vessel insert retains the analyte of interest and facilitates a highly efficient post-extraction recove ry of the analyte. Recoveries of acyclovir were 99% and relative stand ard deviation of 5.3%.