A semi-automated high-performance liquid chromatographic system for the determination of 25-hydroxyvitamin D in human plasma: elimination of interference by barbiturates and use of photodiode array detection.

A semi-automated high-performance liquid chromatographic (HPLC) method for the measurement of 25-hydroxyvitamins D(2) and D(3) is described. Plasma was extracted using acetonitrile and a Bond-Elut C(18) cartridge system, eluted with methanol and fractionated on Sep-Pak SIL. After formation of isotachysterol isomers straight-phase HPLC was carried out monitoring the mobile phase with a photodiode array detection system.