High-performance liquid chromatographic assay for prostaglandin E₁ in various ointment vehicles. Separation and stability testing

A high-performance liquid chromatographic method for the prostaglandin E₁ (PGE₁) incorporated in white petrolatum, white ointment, hydrophilic petrolatum and Plastibase was investigated. The prostaglandin was separated from the oleaginous vehicles with n-hexane-aqueous acetonitrile. Most of white petrolatum, which is a principal component in the vehicles, remained in the n-hexane layer, and the recovery of the drug from any vehicle attained 100%. The method was applied to stability studies of PGE₁ in white petrolatum and macrogol ointment. In which pure PGE₁ and PGE₁-α-cyclodextrin complex (PGE₁-CD) were incorporated. The drug remained intact for up to 6 months when stored at 5°C. At 25 and 40°C, pure PGE₁ was more stable than PGE₁-CD and both PGE₁ species were more stable in white petrolatum than in macrogol ointment.