Determination of methylparaben in o/w emulsions by solid-phase extraction and high-performance liquid chromatography

A simple, fast, and accurate solid-phase extraction (SPE) using a 1-cc Oasis HLB cartridge for sample clean-up followed by an HPLC analysis for the assay of methylparaben (MP) in an o/w emulsion is described. One milliliter of methanol followed by 1 ml of 10% methanol in water was used to activate the cartridge sorbent. The sample was loaded into the cartridge and MP was then separated from oil-soluble excipients by washing the cartridge with 1 ml of 10%, CH3CN in water. MP was finally eluted from the cartridge with mobile phase, acetonitrile and water (60:40), and quantified by HPLC analysis on a Nova-pak(R) C-18 column at 254 nm.