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

Inverse supercritical fluid extraction (SFE) is a new approach to sample preparation. In most cases SFE is used to remove the analyte from the matrix, but in our investigation the analyte was retained in the extraction vessel while the matrix is extracted. Our study investigates the isolation of acyclovir from the pharmaceutical agent Zovirax Ointment 5%. Acyclovir is a polar analyte and is insoluble in 2% methanol-modified 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 aforementioned supercritical fluid. A vessel insert retains the analyte of interest and facilitates a highly efficient post-extraction recovery of the analyte. Recoveries of acyclovir were 99% and relative standard deviation of 5.3%.