Determination of a new calcium antagonist in human plasma by liquid extraction enrichment and HPLC with UV detection

Summary An HPLC method has been developed for the determination of SL 85.1016, a new calcium antagonist arylbenzylamide methylthioether derivative. SL 85.1016 and the internal standard, SL 87.0210, are extracted from alkaline human plasma withn-hexane and back extracted into 0.05 M phosphate buffer (pH 2.5; 0.2 ml). Acetonitrile (50 l) is added to the final aqueous extract in order to prevent absorption of the compounds of interest onto the walls of the glass tube; this solution then is partially processed by HPLC on a C₁₈ column with UV detection (254 nm). The determination limit of the method is 2 ng.ml^–1 of SL 85.1016 in human plasma; the response to the drug is linear in the range 2–200 ng.mg^–1.