Determination of isotretinoin in human plasma by high performance liquid chromatography–electrospray ionization mass spectrometry

A rapid, sensitive and specific high performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method for the quantification of 13-cis-retinoic acid (isotretinoin) in human plasma has been developed. Acitretin was employed as the internal standard (IS). The analytes were chromatographically separated on a Shimadzu Shim-pack VP-ODS C18 column (150 mm × 2.0 mm I.D.) with a mobile phase consisting of acetonitrile and water (90:10, v/v). Detection was performed on a single quadrupole mass spectrometer using an electrospray ionization interface with the selected-ion monitoring (SIM) mode. The method showed excellent linearity (r = 0.9989) over the concentration range of 10–1500 ng/mL with good accuracy and precision. The intra- and inter-batch precisions were within 10% relative standard deviation. The recoveries were more than 80%. The validated method was successfully applied to a preliminary bioequivalence study of isotretinoin in 20 Chinese healthy male volunteers.