A liquid chromatographic-mass spectrometric method for the determination of cortisol in serum using atmospheric pressure electrospray ionization and tandem mass spectrometry is described. During sample preparation, 150 μl of serum were deproteinized with methanol/zinc sulfate followed by on-line solid phase extraction employing column switching. Tri-deuterated cortisol was used as the internal standard. The following transitions were monitored: cortisol, 363>309 m/z; d3-cortisol, 366>312 m/z. The total run-time was 5 minutes. The method proved linear (0–500 μg/l; r=0.999), precise (total coefficient of variation between 5.0% and 3.2% at a mean cortisol concentration of 15.1 μg/l and 269 μg/l, respectively; n=16) and specific with regard to relevant endogenous and exogenous steroids.
Copyright © 2001 by Walter de Gruyter GmbH & Co. KG