On-line solid-phase extraction with automated cartridge exchange for liquid chromatographic determination of lipophilic antioxidants in plasma.

A fully automated liquid chromatographic method is described based on a Prospekt solid-phase extraction unit for the analysis of lipophilic indenoindolic antioxidants in plasma. Plasma samples, mixed with internal standard, were injected onto C8-cartridges. After washing, the samples were eluted and transferred to a C8-analytical column, where separation was performed. The eluent was monitored by electrochemical detection. Owing to the nature of the drugs investigated care had to be taken to avoid adsorption losses in vials and capillaries. The method, which was found to give excellent recoveries (100.9%, n = 8) and repeatability (R.S.D. +/- 1.7%), is time-saving compared to a previously used assay with sample work-up by liquid-liquid extraction.